172 TRANSACTIONS AND PROCEEDINGS OF THE [Skss. Lxvi. 



in his paper on " The Causation of Cancerous Growths," ^ 

 and in a ])rivate communication, acknowledges that what 

 he had, since 1896, called "habit of growth" in certain 

 cells, which ought not to be proliferating then or there, is 

 " based upon that principle of inertia " concerning which 

 he quotes at some length from my original paper.""' 



I had early seen that it must be in virtue of the inertia 

 of protoplasm that certain cells hold on their disastrous 

 course of local growth, utterly oblivious to the vital needs of 

 adjacent tissues, but I did not feel myself entitled to speak 

 on matters pathological with that authority which belongs 

 to a specialist in pathology. I felt sure the principle was 

 capable of wide application, not only to problems in 

 pathology but in embryology (and teratology), and in the 

 study of inheritance in its widest aspects. Functional 

 inertia seems as universal a property of living matter as is 

 the inertia of non-living matter. In my original paper I 

 used the term functional " momentum " as equivalent to 

 katabolic inertia ; I have not persisted in the use of the 

 term, because of the very precise mathematical meaning 

 (|MV") assignable to "momentum"; if, however, momentum 

 be used without this exact signification, and merely as a 

 synonym for " inertia of matter in motion," then there is 

 a functional or protoplasmic momentum. 



All those cases insisted upon by Heidenhain of organs 

 performing their functions, especially glands secreting, 

 either in the absence of blood or after extreme vasocon- 

 striction, are clearly cases of katabolic inertia; the secretion 

 cannot be indefinitely kept up after the blood-supply 

 ( = food-supply) has been cut off, the apparent independ- 

 ence is only temporary, the bloodless protoplasm indeed 

 maintains its secretional status quo ante, but only so long^ 

 as its katabolic inertia persists. Functional inertia ex- 

 presses itself very markedly in the phenomenon known as 

 " latent period " or " physiological lost time." In the case 

 of stimulation of the cardiac Vagus, it is katabolic inertia 

 that is responsible for the " latency." It is very well 

 known that this stimulus does not take effect at once, but 

 that the time of about a beat and a half (frog's heart) may 



I "Brit. Med. Journal," 16th March 1901, pp. 621 and 626. 



" " Brit. Med. Journal," 15th Sept. 1900 (paper read August 1900). 



