THE REPRODUCTIVE GLANDS. 333 



from it, undergoes a cleavage in which a residue rich in iodine 

 remains. The organic iodine compound so obtained which 

 may be the true active principle is called iodothyrin or thyro- 

 iodine. In earlier experiments Baumann, the discoverer of 

 this compound, found an iodine content of about 9 per cent, 

 but Oswald, starting with pure iodothyreoglobulin which was 

 secured by a salting-out process with ammonium sulphate, 

 obtained finally iodothyrin with over 14 per cent of combined 

 iodine. This iodothyrin is not a protein substance ; the analy- 

 ses of different preparations are not in very good accord, from 

 which it appears that the pure substance has not yet been 

 actually secured. The crude product at present known has 

 been used in medicine and attempts have been made to dupli- 

 cate or replace it by other iodine compounds. 



The administration of iodine salts increases the iodine con- 

 tent of the thyreoglobulin in animals. It has also been shown 

 that extracts from the gland, or the iodothyrin when adminis- 

 tered hypodermically, counteract the bad effects of the re- 

 moval of the gland or the effects of its degeneration. The 

 therapeutic uses depend on these observations. 



The other extractive bodies found in the thyroid are not 

 important. Several of the purine derivatives seem to be pres- 

 ent ; also lactic and succinic acids and amino acids, probably as 

 degeneration products. The thymus gland of the calf is said 

 to resemble the thyroid in containing a little iodothyrin. 



THE REPRODUCTIVE GLANDS. 



Of the chemical composition of the testicles and their secre- 

 tion not much can be said. The testicles contain several pro- 

 teins and extractives, but their investigation has been ex- 

 tremely limited. The most complete examinations of the 

 spermatic fluid are probably those reported by Slowtzoff, from 

 whose work the following figures are taken. The specific 

 gravity of the fluid varies from 1.02 to 1.04; the reaction is 

 alkaline and as measured by the aid of rosolic acid corresponds 

 to 0.15 per cent sodium hydroxide. As a mean of five analy- 

 ses the following results may be given : 



