“ The power to regulate existing, the details of the legislation and the exceptions proper to be made rest primarily within the discretion of the state legislature, and 'unless such regulations are so unreasonable and extravagant as to interfere with property and personal rights of citizens, unnecessarily and arbitrarily, they are within the power of the state ”

“ No person, firm, or corporation, or any agent thereof, other than a national bank or a bank or trust company duly incorporated under the laws of this state, or a pawnbroker, as provided in chapter 235 of the Public Acts of 1905, shall, directly or indirectly, loan money to any person, and directly or indirectly charge, demand, accept, or make an agreement to receive therefor interest at a greater rate than 15 per centum per annum. ”

“ In the argument for plaintiff in error no reference is made to the claim urged below of the protection of the contract clause of the Constitution. The claim appears to have had reference to a provision contained in § 5 of the act of 1907, forbidding the enforcement of contracts made in violation of the act, thereby operating to deny validity to such contracts when made by those not within the exempted classes. ”