15(> NERVE PROTOPLASM GIVES ALL 



genous the diet be. Independently of this, the ex- 

 cretion of urea is almost entirely regulated in health 

 by the quantity of nitrogenous matter in the diet, no 

 matter the amount of muscular work done. Thus, the 

 immediate source of muscular, as of all other work 

 and every other vital act, may be the decomposition of 

 a nitrogenous compound, such as protoplasm, yet from 

 the harmony and perfection of the working of the 

 organism as a whole, the most perfect economy in 

 extracting the force of the food is attained by the 

 excretion of only the spent products of the diet, what- 

 ever its nature. 



The question now is, where do all these processes 

 take place in the muscle ? The parenchyma is now 

 pretty well explored, and there are no considerable 

 territories still unknown in which these operations 

 may take place. According to Beale, the change of 

 matter must take place in the protoplasm, but the bulk 

 of the muscles, i.e., the fibres, do not consist of proto- 

 plasm and are not living, nor is the power evolved in 

 the bioplasts of the muscular fibre. There remains 

 only, therefore, the protoplasm of the motor nerves or 

 of the capillaries or of the connective tissue. The proto- 

 plasm of the capillaries (venous at least) is no doubt 

 fully occupied in the recomposition and absorption 

 into the blood of the products of change, and the con- 

 nective tissue corpuscles are too insignificant to be 

 taken into account. Therefore, we are compelled to 

 fall back upon the protoplasm of the intra-muscular 

 motor nerves (and, possibly, to some extent, the bio- 

 plasts of the arterial capillaries) as the source of the 

 whole poiver of muscular motion, and unless there is- 



