14 INTERNAL SECRETION 



living substance and therewith a restitution of provision for 

 labour. With the cessation of the disassimilatory stimulus assimi- 

 lation becomes excessive and, if the process is frequently repeated, 

 the well-known phenomena of organic hypertrophy will make 

 their appearance. 



Some experiments by Kronecker and Cutter are interesting 

 in this connection. These authors found that, after the exercise of 

 the lower extremities by mountain climbing, the upper extremities, 

 which did not participate in the exercise, showed a perceptible 

 increase in the development of the biceps group. This increased 

 capacity for labour without previous direct exercise of function, 

 which, by repetition of the same process, would certainly lead 

 to a " labour-hypertrophy without labour," can only be accounted 

 for in one way. The assumption is that, by means of a chemical 

 agent, a secondary increased assimilatory growth takes place in 

 organs which are not affected by the disassimilatory decom- 

 position. 



That inhibition of function of certain organs may be due to 

 the intervention of the nervous system is, of course, admitted, 

 but we now know that such inhibition may also be induced by 

 chemical substances. This is readily explained by a combination 

 of increased assimilation with one of decreased disassimilation ; 

 while, by reversing the process, we account for the existence of 

 organic activity. Some years ago the physiologist, W. Gaskell, 

 pointed out that, if we assume an assimilatory activity on the 

 part of the vagus nerve, its effects are no more mysterious and 

 inexplicable than are those of the motor-nerves in their character 

 of stimulants of disassimilation. As a matter of fact, there is 

 considerable ground for the belief that the chemical changes 

 brought about in the heart muscle by the agency of the vagus 

 are assimilatory in their nature. Thus, after vagal irritation, 

 there is increased muscular power and capacity for work and an 

 improved conduction of stimulus, especially of the positive current 

 oscillation. This positive current oscillation is the antithesis of 

 the negative current oscillation, which is due to intervention of 

 the motor-nerves and is to be regarded as a symptom of dis- 

 assimilation. 



By inhibitory hormone, then, w r e understand a chemical agent 

 which excites an assimilatory process in another organ. The 

 increased activity (muscular contraction, secretion, &c.) which 

 follows the suppression of a hormone, is to be regarded as a sign 

 of the unchecked disassimilation consequent upon such suppres- 

 sion. 



The method of classification, as defined above, does not 

 pretend to be more than the outline of a plan into which the 

 greater number of details have still to be fitted. The data which 

 we possess are very scanty and, in many directions, are in need 

 of revision. 



