Lepidosteus

“ Lepidosteus is very remarkable for the great number of mesoblast cells which thus enter the cavity of the vitreous humour, and for the fact that these cells are at first unaccompanied by any vascular structures (Plate 37, fig. 43, v.h) . The mesoblast cells are scattered through the vitreous humour, and there can be no doubt that during early larval life, at a period however when the larva is certainly able to see, every histologist would consider the vitreous humour to be a tissue formed of scattered cells, with a large amount of intercellular substance ”

“ Lepidosteus is a voracious Fish, preying upon smaller Fishes, and, except in the breeding season, it frequents the deeper parts of the rivers or lakes. The Fish is constantly in the habit of rising to the surface and emitting bubbles of gas, either through the mouth or by the branchial clefts, and it is probable that this gas is air which has been previously swallowed at the surface and passed into the air-bladder. ”

“ It is important to notice that this cleft, which in the cartilaginous Ganoids and Polypterus remains permanently open as the spiracle, is rudimentary even in the embryo of Lepidosteus.
The second pouch is the hyobranchial pouch: its outer end meets the epiblast before the larva is hatched, and a perforation is effected at the junction of the two layers, converting the pouch into a visceral cleft. ”

“ It is easy to conceive that the ribs in the trunk might somewhat alter their position by passing into the muscles, along the inter-muscular septa, till they come to lie between the dorso-lateral and ventro-lateral muscles, as in Elasmobranchii. Lepidosteus itself affords a proof that such a change in the position of the ribs is not impossible, in that it differs from other Ganoids and from Teleostei in the fact that the free ends of the ribs leave the neighbourhood of the body-cavity and penetrate into the muscles. ”

“ Our own observations go far to confirm Agassiz' opinion.
Apart from the complete segmentation, the general development of Lepidosteus is strikingly Teleostean. In addition to the general Teleostean features of the embryo and larva, which can only be appreciated by those who have had an opportunity of practically working at the subject, we may point to the following developmental features [551] as indicative of Teleostean affinities:—
(1) The formation of the nervous system as a solid keel of the epiblast. ”

“ In Lepidosteus the Müllerian duct appears to have become attached to the generative organs, so that the generative products, instead of falling directly into the body cavity and thence entering the open end of a peritoneal funnel of the excretory organs, pass directly into the Müllerian duct without entering the body cavity. In most Teleostei the modification is more complete, in that the generative ducts in the adult have no obvious connection with the excretory organs. ”

“ Fig. 61. Embryo of Lepidosteus on the sixth day after impregnation.
op. optic vesicles; br.c. branchial clefts (?) ; s.d. segmental duct.
N.B. The branchial clefts and segmental duct are somewhat too prominent.
The mesoblast of the trunk is divided anteriorly into splanchnic and somatic layers.
In the next stage, on the sixth day after impregnation (fig. 61) , there is a great advance in development. The embryo is considerably longer, and a great number of mesoblastic somites are visible. The body is now laterally compressed and raised from the yolk. ”

“ Fig. 293. Section through the front part of the head of a Lepidosteus embryo on the seventh day after impregnation.
al. alimentary tract; fb. thalamencephalon; l. lens of eye; op.v. optic vesicle. The mesoblast is not represented.
Up to the eighth day the pecten remains as a simple lamina; by the tenth or twelfth day it begins to be folded or rather puckered, and by the seventeenth or eighteenth day it is richly pigmented and the puckerings have become nearly as numerous as in the adult, there being in all seventeen or eighteen. ”

“ A peculiar feature of the North American Fish Fauna is that it has retained, besides the Sturgeons and Lampreys, representatives of two Ganoid families, Lepidosteus and Amia. Both these genera existed in tertiary times: the former occurs in tertiary deposits of Europe as well as North America, whilst fossil remains of Amia have been found in the Western Hemisphere only.
It is difficult to account for the presence of the Amiurina in North America. They form a well-marked division of the Bagrina, which are well represented in Africa and the East Indies, but absent in South America ”

“ The young already have also the peculiar habit of the adult of coming to the surface to swallow air. When they go through the process under water of discharging air again they open their jaws wide, and spread their gill-covers, and swallow as if they were choking, making violent efforts, until a minute bubble of air has become liberated, when they remain quiet again. The resemblance to a Sturgeon in the general appearance of this stage of the young Lepidosteus is quite marked. ”

“ Indications of transition are not wanting in the squamation in certain families, and may be seen in the partial or complete replacement of the rhombic type by thin, imbricated, cycloid scales. Lastly, the soft parts of the two surviving genera are not without features of similar significance. A multivalvular conus arteriosus, it is true, is still retained, but the spiral valve is vestigial, the spiracles are closed, and in the female of one genus (Lepidosteus) the gonoducts are peritoneal tubes, continuous, as in most Teleosts, with the investments of the ovaries. ”

“ In the skull of Lepidosteus the cartilage of the endocranium is still more replaced by ossifications than in Polypterus; those ossifications, moreover, being represented by a greater number of discrete bones; especially the membrane-bones are greatly multiplied: the occipital, for instance, consists of three pieces the vomer is double as in Polypterus; the maxillary consists of a series of pieces firmly united by suture. The symplectic reaches the lower jaw, so that the articulary is provided with a double joint, viz. ”

“ I have observed the development of the posterior roots in Lepidosteus, in which they appear as projections from the dorsal angles of the spinal cord, extending laterally outwards and, at first, having their extremities placed dorsally to the muscle-plates.
Fig. 270. Transverse section through the posterior part of the head of an embryo chick of thirty hours.
hb. hind-brain; vg. vagus nerve; ep. epiblast; ch. notochord; x. thickening of hypoblast (possibly a rudiment of the subnotochordal rod) ; al. throat; ht. heart; pp. body cavity; so. somatic mesoblast; sf. splanchnic mesoblast; hy. ”

“ The thigh or ham has been mentioned by some authors as the principal seat of these vesicles, but they are also found on the shoulders, around the jaws, along the neck and belly, and even underneath and around the root of the tongue, where alone can any outward lesions indicative of leprosy be in general discovered; and even here they are not constant, out are chiefly evident in those animals in which the disease has attained to a great height. The progress of leprosy is very insidious, and the early symptoms so little marked that a practised eye only can detect them. ”

“ LEPROSY (Lepra Arabum, Elephantiasis Graecorum, Aussatz, Spedalskhed) , the greatest disease of medieval Christendom, identified, on the one hand, with a disease endemic from the earliest historical times (1500 B.C.) in the delta and valley of the Nile, and, on the other hand, with a disease now common in Asia, Africa, South America, the West Indies, and certain isolated localities of Europe. An authentic representation of the leprosy of the middle ages exists in a picture at Munich by Holbein, painted at Augsburg in 1516 ”

“ There is perhaps no subject of greater interest, nor one which awakens more sympathy, than that of the Leper; it affords a most curious, though painful topic of enquiry, particularly in the present day, when so much has been said and written, as to the probability and possibility of the loathsome scourge again obtaining a hold in this, our own country.
Much confusion and ignorance exists, as to what true Leprosy really is. I do not pretend, nor do I assume, to be in any way an authority on the disease, nor to be at all deeply versed in the matter ”

“ Physicians write that there are three sorts of Leprosies; namely, Tyria, from the serpent Tyrus. In this leprosy, the patient’s skin is soft, and sometimes falleth off in shells, and they have many spots and white wartes thereon. The second is called Alopecia, by reason the hairs fall off as those of a fox; he that is infected with this leprosy hath a red face, and his beard and eyebrows fall off. The third sort is called Elephantiasis, from the elephant, to whom they become like in their skin; the body and face of him that is infected with this disease is full of knobs. ”

“ The leprosy of the Icelanders (Likthra, Holdsveike, or Spitelska) , exhibits in many instances all the essential characters of the genuine elephantiasis or Lepra Arabum; and is a disease of the most formidable and distressing kind. Indolent tumours of the face and limbs are, generally, among the first symptoms of the complaint, attended by swellings of the salivary, inguinal, and axillary glands. The nostrils, ears, and lips are progressively affected with swelling deformity. The skin over the whole, or different parts of the body, becomes thick and hard ”

“ The so-called white [leprosy] shows the difference between assimilation and adhesion, in the same way that the kind of dropsy which some people call anasarca clearly distinguishes presentation from adhesion. For, of course, the genesis of such a dropsy does not come about as do some of the conditions of atrophy and wasting, from an insufficient supply of moisture; the flesh is obviously moist enough,—in fact it is thoroughly saturated,—and each of the solid parts of the body is in a similar condition. ”

“ We have indeed sought above to point out the possibility that the lepra bacillus is attenuated in the maculo-anæsthetic form of the disease; but we know of no phenomenon which would allow us to assume that the bacillus could occasionally become quite innocuous, and call forth no symptoms of disease.
All this, however, proves nothing against the hypothesis; and it is always a dangerous thing to use a simple absence of knowledge either to contradict or to found a hypothesis. ”

“ The question as to heredity now is, Can the lepra bacillus be conveyed by heredity. This is Baumgarten’s view; he holds that both Tuberculosis and Leprosy are thus spread, that the bacilli of both diseases may be transferred to the children and there remain dormant, but that they can thence be conveyed to another generation, and from it to a fourth, fifth, etc. generation, and then in the third, fourth, etc. generation become once more active and cause the disease. ”

“ Armauer Hansen discovered the bacillus leprae in 1871, but no one has gotten much further than that. Its only alleviation is surgery, but this is sometimes without avail. Leprosy is of three well-defined kinds: There is Running Leprosy, the most horrible of the three. It shows itself mainly as shiny ulcers, which throw off a highly offensive perspiration. In this kind, the fingers, ears, nose, and eyes are often eaten away, leaving a hideous bundle of flesh that but faintly resembles a human being. Dry Leprosy, the second variety, does not take such an offensive form. ”

“ It is there mentioned that leuce is Celsus’ third species of vitiligo, and the baras of all the Arabian translators, with the exception of Stephanus Antiochensis, the translator of Haly Abbas, who applies the term lepra to it. It was therefore the white species of leprosy. All the medical authorities represent it as an intractable disease, not only the cuticle being altered in structure, but also the flesh below, and even the hairs, having undergone a change of colour. All direct us to prick the skin with a needle, and, if it bleed, the cure is to be attempted ”

“ The larva of Atherix has seven pairs of abdominal feet. Altogether there are some two or three hundred known species of Leptidae; our British species scarcely reach a score. They are destitute of biting-powers and are harmless timid creatures. Leptis scolopacea, the most conspicuous of our native species, a soft-bodied fly of rather large size, the wings much marked with dark colour, and the thick, pointed body yellowish, marked with a row of large black spots down the middle, is a common Insect in meadows. ”

“ Weak or diseased examples may be chiefly selected. The flexible Leptoplana adheres firmly to its prey, and the rapid action of the salivary glands of its mobile pharynx quickly softens and disintegrates the internal parts of the victim. The food passes into the stomach (Fig. 2, mg) , and is there digested. It is then transferred to the lateral branches of the intestine, and, after all the nutritious matters have been absorbed, the faeces are ejected with a sudden contraction of the whole body through the pharynx into the water. ”

“ Taking into consideration this marked prevalence of Corrosion of the Shin-bones, we might argue with considerable probability that it pointed to the existence of a disease of the bones following as a result of vicious indulgence. On the other hand the observation that the precise time the body became covered with ulceration was after indulgence in fish-eating cannot help being of weight in connection with the doctrine of Leprosy; for to the present day we note as very frequent among peoples whose chief nutriment is fish various forms of Leprosy. ”