IN MEDICAL SCIENCE. 41 



vailing law of the organism. Nutrition itself is but one 

 great catalytic process. As the blood travels its rounds, 

 each part selects its appropriate element and transforms 

 it to its own likeness. Whether the appropriating agent 

 be cell or nucleus, or a structureless solid like the in- 

 tercellular substance of cartilage, the fact of its pres- 

 ence determines the separation of its proper constitu- 

 ents from the circulating fluid, so that even when we 

 are wounded bone is replaced by bone, skin by skin, 

 and nerve by nerve. 



It is hardly without a smile that we resuscitate the 

 old question of the vis insita of the muscular fibre, so 

 famous in the discussions of Haller and his contempo- 

 raries. Speaking generally, I think we may say that 

 Haller's doctrine is the one now commonly received ; 

 namely, that the muscles contract in virtue of their 

 own inherent endowments. It is true that Kolliker 

 says no perfectly decisive fact has been brought for- 

 ward to prove that the striated muscles contract with- 

 out having been acted on by nerves. Yet Mr. Bow- 

 man's observations on the contraction of isolated fibres 

 appear decisive enough (unless we consider them inval- 

 idated by Dr. Lionel Beale's recent researches, tending 

 to show that each elementary fibre is supplied with 

 nerves *) ; and as to the smooth muscular fibres, we 

 have Virchow's statement respecting the contractihty 



* Proc. Eoyal Society, No. XL. Vol. X., and British and Foreign Med. 

 Chir. Review for April, 1861. 



