i68 INTERNAL SECRETIONS 



present, there are no intermediate stages in regard to develop- 

 ment of sexual characters; they are either fully developed or 

 else they are in the same state as in the "castrate." Pezard 

 suggested that the hormonic action of the sex gland is regulated by 

 the law of "All or Nothing," applied already in the case of the 

 heart (Marey) and nerve (Lucas and Adrian, Verworn, Veszi), 

 and probably true also for skeletal muscle (Lucas, Adrian). This 

 law afhrms that when the strength of the stimulus is increased 

 beyond that of the liminal or threshold stimulus the effect is 

 not varied {Fig. 90). The difference between the suggestion of 

 Pezard and that developed by myself in the first edition of this 

 book and represented in the above diagram {Fig. 89) is, that 

 according to Pezard only the horizontal part of this curve is 

 correct and, further, that this horizontal part must be much 



2% 100 % 



thr. 11. 



Fig. go.^Diagram to illustrate the law of "All or Nothing." The maximal 

 hormonic effect (ordinates) is brought out when the threshold quantity 

 (thr) of sex hormones is produced. The threshold quantity is supposed 

 to be very small as compared with the average normal quantity {n), 



displaced to the left. Our own experiments with partial castra- 

 tion justify us in discussing this quantitative problem more fully. 

 In confirmation of Pezard's statements on fowl we have showoi 

 in mammals that the testicular particles which can admit of 

 full development of somatic sexual characters may be so small 

 that it is impossible to lay down any practical Hmit to the 

 minimal quantity sufficient for the growth of the sexual char- 

 acters. In other words, the horizontal part of the curve will 

 begin not far from o, in our experiments near one per cent, or 

 even less. But this does not necessarily imply that no pro- 

 portionality between hormonic quantity and hormonic effect 

 exists in the limits between o and one per cent. In our 



