500 PROCESSES INFERRED FROM INDIRECT OBSERVATION 



centrated extract of the tissue, representing a much larger dose of the 

 fresh tissue than would be practicable to employ. The Posterior Lobe 

 of the pituitary is but poorly supplied with bloodvessels and hence the 

 active material which it elaborates accumulates in the tissue and very 

 minute doses of posterior-lobe tissue or extract are capable of eliciting 

 the characteristic effects of Pituitrin upon smooth muscular tissue. 



The Pineal Gland is stated by McCord to have a decisive influence 

 upon the growth of the Secondary Sexual Characters. Tumors of the 

 pineal gland have not infrequently been described, and are usually 

 associated in children with extraordinary precocity of sexual develop- 

 ment. Either, therefore, the pineal gland elaborates a principle which 

 directly and specifically accelerates the growth of the secondary sexual 

 characters, or else it operates indirectly, by stimulating the interstitial 

 cells of the ovary or testes. 



The relationship of the Nervous Tissues to the growth of the whole 

 organism is one which can by no means be overlooked in this connec- 

 tion. It is, indeed, not at all improbable that the nervous system 

 performs the dual role of a conducting and coordinating mechanism and 

 a factory of endogenous catalyzers of growth. As we shall see, the 

 growth-catalyzers of which we have positive knowledge, Cholesterol, 

 Lecithin and Tethelin, are all lipoidal in character and these substances, 

 or substances related to them, are exceedingly abundant in nervous 

 tissues. We cannot suppose that the substances which contribute to 

 the building up of nervous tissues or result from their degeneration are 

 not abundant in the circulating fluids in proportion to the development 

 of the nervous tissues or the ratio of their mass to that of the whole 

 body, and several of them we know to exert, and others we may 

 reasonably suspect of exerting, effects analogous to catalysis upon the 

 growth of other tissues. The development of the nervous system may 

 thus be instrumental in determining the development of the whole body. 



THE METABOLIC RATE AND THE PARTITION OF NUTRIENTS. 



The loss of weight which occurs in Starvation is by no means uni- 

 formly distributed throughout the body. The following table displays 

 the loss of substance, in percentages of the normal weight, of the 

 various tissues of cats after death from inanition : 



Loss of weight, 

 Tissue or organ. per cent. 



Fat 97 



Spleen .67 



Liver .54 



Testes :..;... 40 



Muscles 31 



Kidneys 26 



Skin . ' 21 



Intestine 18 



Lungs . ! . . 18 



Pancreas ..,%..:..... 17 



Bones ........ 14 



Heart . ... . .'. ........... 3 



Central nervous system . 



