TRANSMISSION OF MODIFICATIONS 38-3 



Chemical action of normal secretions. In the opinion of the 

 writer, those who discuss the subject of the transmission of 

 modifications (acquired characters) as if it were a single issue, 

 and dismiss it in toto as impossible upon the theoretical ground 

 that no such modifications could by any manner of means affect 

 the germ plasm those who discuss and dismiss the matter in 

 this manner commit a fundamental error in overlooking the 

 fact that, as a whole, this is a broad question, or rather a series 

 of questions, and that the living organisms, exposed as they 

 are for generations to outside conditions absolutely essential to 

 their existence, present many points of contact in which they 

 are exceedingly susceptible to influence. They make the fatal 

 error, too, of failing to distinguish between those circumstances 

 that affect only the externals of the body and those all-pervading 

 influences that affect the very constitution of the organism. 



For example, it is now well known that the perfect working 

 of the body as a whole depends upon the presence of specific 

 secretions of certain organs, many of which were once thought 

 to be functionless. Destruction of the thyroid gland at once 

 arrests not only the physical but the mental development. In 

 children its degeneration results in retarded mental development 

 and even in idiocy, a calamity that can be ameliorated, and even 

 averted, by the injection of thyroid substance of animals. Bau- 

 mann found that the secretions of this gland are characterized by 

 the presence of iodin, which is found nowhere else in the body. 1 



On this same general question Vernon, after speaking of the 

 frequently fatal effect of removing the thyroid gland, unless the 

 animal be fed thyroid substance, remarks as follows : 2 



Extirpation of the suprarenal glands results in much more speedy death, 

 and here again the injection of extracts may delay the fatal issue. Extir- 

 pation of the pancreas causes the production of severe diabetes, and ulti- 

 mately death, but such an effect may be avoided by the grafting of a 

 portion of excised gland in the peritoneal cavity or the tissues. . . . Again, 

 extirpation of the total kidney substance of the dog leads, not to a dimin- 

 ished secretion of urine, but to a largely increased secretion, accompanied 

 by a rapid wasting away, which soon ends fatally. Hence the kidneys may 

 possess an influence on the metabolism of the whole body, as well as their 



1 Loeb, Physiology of the Brain, pp. 207-208. Extracts of this and other 

 glands are now regularly prepared at our larger slaughterhouses. 



2 Vernon, Variation in Animals and Plants, pp. 358-360. 



