20 FUNCTIONAL INERTIA 



Passing on to tissues, we have the familiar latent 

 period of muscular tissue, shortest for striated muscle 

 of warm-blooded animals, longer for heart-muscle, 

 longest of all for non-striated fibre. In other words, 

 the fibre with least anabolic inertia has most affect- 

 ability (striated), that with most inertia has least 

 affectability (non-striated), and heart-muscle occupies 

 an intermediate position. As judged by the duration 

 of post-mortem life, a point which will be discussed 

 later on, the non-striated fibre has most and the 

 striated least katabolic inertia, the myocardium 

 again occupying an intermediate place. 



(I have seen a frog's heart beating after four 

 minutes' immersion in " Ranvier's j- alcohol.") 



Latent period undoubtedly exists in other tissues 

 of the animal in gland, and in the nerve-cells, 

 both of spinal cord and of cerebrum.* 



In all cases in which the stimulus is nerve-impulses 

 which have travelled through any length of nerve 

 before impinging on the tissue in question, the true 

 latency of the tissue is the difference between the 

 total physiological lost-time and the time taken by 

 the impulse to travel from the point of origination to 

 the nerve-endings in fibre or cell. 



The latent period for secretion by the pancreas 

 through stimulation of the vagus, e.g., is very long 

 (15" to 3', Pawlow). Now the time of travelling of 

 nerve-impulses is very short (at least 30 metres a 

 second) so that even when the time for transit through 



* Gotch, "Text-book of Physiology." Edited by Schafer, 

 Vol. ii. chap, on " Nerve/' p. 451. 



