488 



Mr. H. Tomlinson. The Influence of 



Third. That they participate in all the changes the mesentery 

 undergoes. 



Fourth. That if an organ is developed in the mesentery or from the 

 gut, it obtains, part at least, of its vascular supply from 

 the vessels of the mesentery, or from those of that part 

 of the gut from which it sprung. 



These principles have, in this paper, only been applied to the 

 development of the blood-vessels of the human alimentary canal, but 

 they seem so simple, and the probability of their truth appears so 

 great, that it may be anticipated that they will be found of very much 

 wider application. 



" The Influence of Stress and Strain on the Physical 

 Properties of Matter.* Part I. Moduli of Elasticity— 

 continued. Relations between Moduli of Elasticity, Thermal 

 Capacity, and other Physical Constants." By Herbert 

 Tomlinson, B.A. Communicated by Professor W. Grylls 

 Adams, M.A., F.R.S. Received May 28, 1884. Read 

 June 19. 



It has been proved by Wertheim,f whose results have been verified 

 by myself, J that if e be taken to denote " Young's Modulus," and a. 

 the mean distance between the centres of any two adjacent molecules 

 of a solid body, e x a 7 is, in the case of most metals, approximately a 

 constant. Poisson, regarding a body as an assemblage of molecules 

 very small as compared with the distance between them, bound to 

 one another by an attractive force, and kept at a distance by the 

 repulsion due to heat, was led to the formula — 



£ 3 a 5 dr 



r—a. 



In this formula N is a constant force perpendicular to the surface 

 of the body, B the corresponding linear expansion or contraction pro- 

 duced, r the radius of activity of a molecule, a the mean distance 

 between two adjacent molecules, and fr the function by which the 

 law of the resultant molecular force is expressed. It follows, there- 

 fore, that if e X a 7 is a constant, fr must decrease in the inverse 



* The original title of the paper has been altered to the above as being more exact 

 in expression. 



f " Ann. de Chimie," 1884, torn. xii. 

 X " Phil. Trans.," Part T, 1883, p. 32. 



