18 Mr.Woolhouse ott the Theory of Vanishing Fractions, 



At the foot of page 1 66, your botanical friend asks me if 

 I have ever tried the effect of division on Dirca palustris, or 

 on any plant of the natural order Thymelece. 



The Dirca palustris is an exotic, and, I believe, a rare plant, 

 which never having seen, I have of course not had an oppor- 

 tunity of making it the subject of experiment. 



Belonging to the natural order ThymelecE there is one 

 genus only found in England*, the genus Daphne, and of this 

 I have, during the present month, had an opportunity of ex- 

 amining two species, the Daphne Mezereum and Daph. Lau- 

 reola. On dividing the recent green shoot of this year I found 

 it in both decidedly divergent. They form, therefore, no ex- 

 ception to anything which I have stated in my paper. 



At page 169, your medical friend remarks, that the phae- 

 nomena described in my paper most closely resemble the con- 

 traction of the ligamentum nuchse by which the head of ani- 

 mals is retracted after death, and which Bichat attributes to 

 vital contractility. 



Not having, at present, access to the works of Bichat, I am 

 unable to learn the evidence on which he grounds this opinion. 

 Whether true or not, however, I do not see that it affords 

 an objection to anything which I have advanced. 



If this contraction of the ligamentum nuchas be an instance 

 of vital contractility, and susceptible of excitation by stimuli, 

 it would appear to me to be identical with the irritability or 

 contractility of muscular parts, and ansXogoMs io divergence : 

 and therefore not a " distinct property." 



If stimulants do not excite contraction in the ligamentum 

 nuchas, the property, whether vital or not, on which its mo- 

 tions depend, differs in this essential particular from diver- 

 gence. I am, Gentlemen, yours, &c. 



Shrewsbury, May 28, 1836. Henry Johnson, M.D. 



VI. On the Theory of Vanishing Fractions, in Reply to Pro- 

 fessor Young. By Mr. W. S, B. WooLHousE.f 



"1^7"HEN Professor Young's first letter on the theory of 

 '* vanishing fractions made its appearance in the April 

 Number of the Philosophical Magazine, the anomalous ob- 

 jections that were urged against my general principles with 

 such apparent confidence were accounted for in my mind by 

 the belief that he had been carried away by a partial and 

 very imperfect perusal of the contents of my essay. Professor 



* Gray's Natural Arrangement of British Plants. 

 + Communicated by the Author. 



