4i6 



A MANUAL OF VETERINARY PHYSIOLOGY 



can be effected is by employing suitable resistance gradually and 

 skilfully increased. Herein lies the art of the trainer, which 

 requires a long education. The physiologist can control the 

 process, for apart from gross errors in training, such as lead to 

 horses refusing their food, there is the index afforded by the 

 pulse and respiration as a measure of the progress made. In the 

 following table is shown the mean of forty-five observations* on 

 fit and a similar number of unfit horses performing identical 

 work and carrying the same weight : 



The table shows that the pulse and respirations of fit horses are 

 less disturbed by work, and more rapidly subside to normal 

 after work, than of those unfit. In the above series the heart 

 and respiration rate of the ' fit ' subsided in two minutes to a 

 point only reached by the ' unfit ' in five minutes. 



Chemical Composition of Muscle. — A dead muscle does not 

 possess the same chemical composition as one which is living, and 

 living muscle cannot be analysed without killing it by the methods 

 necessarily employed. Thus any tabular statement of the 

 quantitative composition of muscle gives really the composition 

 of dead muscle. We are, however, assisted to some knowledge 

 of the nature of living muscle-substance by the following facts : 

 If contractile, and therefore living, frog's muscle is carefully 

 frozen and then very slowly thawed, it does not lose its irrita- 

 bility : it is still alive. When frozen it may be minced with a cold 

 knife and ground up in a cold mortar with four times its weight 

 of snow containing i per cent, of sodium chloride. By this 

 process a viscid liquid is obtained which may be filtered, though 



* Made for the writer by Captain Wadley, A.V.C. 



