IODINE IN THE ANIMAL ORGANISM. 457 



In the sheep's thyroid, the percentage of iodine varies 

 from 0'9 to 1*5 in the dry, and from 0*26 to 0*44 in the 

 fresh organ. 



In dog's thyroid little or no iodine is found ; but the 

 amount is increased by feeding on dog-biscuit. This fact 

 together with the almost complete absence of iodine in the 

 thyroids of children makes an impartial onlooker rather 

 sceptical concerning thyro-iodin as the essential chemical 

 substance in the internal secretion of the thyroid. 



Nevertheless Roos 1 maintains, and supports his con- 

 tention with numerous and exhaustive clinical records, that 

 this substance acts both in men and animals just like 

 thyroid extracts, or feeding on the gland. The resemblance 

 is seen in its action on the general system, in metabolic 

 processes, and in cases of disease (myxcedema and 

 psoriasis). 



Other observers have not been so fortunate. Thus 

 Gottlieb 2 found in dogs after thyroidectomy that the 

 administration of thyro-iodin had no influence in preventing 

 the symptoms (convulsions, etc.) that follow this operation, 

 nor in delaying death. 



Auerbach 3 suggests that this is because Gottlieb's pre- 

 parations were poor ones ; they only contained 2 "8 per cent, 

 of iodine. 



The main practical question is therefore unsettled, and 

 must be left to future investigations to decide. 



But as a point of scientific interest, the discovery of 

 iodine in the animal body remains as one of great im- 

 portance, and is the most startling of scientific discoveries 

 made of recent years in the domain of chemical physiology. 



Iodine in the thyroid is, however, not a unique occur- 

 rence. Almost simultaneously with Baumann's announce- 

 ment, Drechsel 4 published a paper in which he showed 

 that iodine occurs in other structures in quite a different 

 part of the animal kingdom. 



1 Zeit. physio!. Chem., xxii. p. 18, 1896. 



2 Deutsch. vied. Wochenschr. xxii., 15, p. 235. 



3 Centralbl. f. physiol., x., p. 133, 1896. 



4 Zeit. f. Biol., xxxiii., p. 85, 1896. 



