108 INTERNAL SECRETION 



function in the causation of tetany. For this reason, his doctrine 

 represents a step backwards, and, though the risk of post-operative 

 tetany is now, happily, much less than formerly, the acceptance 

 of Blum's theory might very conceivably add to the seriousness 

 of that risk. 



The arguments which have been brought forward, and the 

 observations which have been described, demonstrate very clearly 

 the erroneous nature of Blum's theory of the antitoxic activity of 

 the thyroid gland. At the same time, these results show that the 

 function of the thyroid gland is, by means of its internal secretion, 

 to supply a chemically active substance to the economy. What is 

 the nature of the specific activity of the thyroid secretion ? The 

 theory advanced by Baumann and his pupils and, more par- 

 ticularly, by Oswald, is based upon the assumption that the 

 specific activity of the colloid present in the thyroid secretion is 

 directed to the neutralization of toxic substances, and that this 

 neutralization takes place within the blood-stream. This is a 

 combination of the theories of secretion and of neutralization. All 

 attempts to obtain this toxin from the blood of thyroidless animals 

 has, however, been attended by as little success as the search 

 for the toxin of tetany. 



The evidence in favour of a neutralizing function on the 

 part of the thyroid gland is wholly indirect. It has been pointed 

 out that thyroidectomized animals have a smaller resistance to 

 inorganic poisons (calomel, according to Perrin and Jeandelize) 

 than normal animals, and that experimentally induced tuberculous 

 and post-tuberculous processes are favourably influenced by pro- 

 longed exhibition of thyroid extract (Frugoni and Grixoni). 



The most important evidence in favour of an antitoxic activity 

 on the part of the thyroid gland and the thyroid substances, is 

 supplied by Reid Hunt's investigation of the neutralization of 

 cyanmethyl (acetonitril, CH 3 CN). He showed that, after the 

 exhibition of a minimal quantity (i/io mg. of the dry gland) of 

 thyroid extract by the mouth, the resistance of white mice to the 

 subcutaneous injection of acetonitril was increased from two- to 

 ten-fold. Thyroid gland which is free from iodine exercises a 

 certain amount of influence in this direction, but as a general 

 rule the neutralizing activity of thyroid extract increases in direct 

 proportion to its iodine contents. It is, however, hardly possible 

 that the process of neutralization consists in a chemical com- 

 bination of the cyanogen components with the sulphur present 

 in the gland. For, in the first place, the thyroid substances do 

 not neutralize the other cyanogen compounds, such as hydro- 

 cyanic acid and sodium nitrocyanide ; and in the second place, the 

 amount of acetonitril neutralized bears no relationship to the 

 amount of thyroid substances. 



Reid Hunt himself points out that the results of his 

 experiments cannot be regarded in any sense as proofs of the 



