278 



ON THE NUTRITION OF 



The circumstance to which I wish chiefly to call 

 the attention of the Society, is, That physiologists 

 seem to have had their views in some degree fetter- 

 ed, by entertaining too strict ideas of the connec- 

 tion between the circulation of fluids and nutrition. 

 It is in cases in which the circulating apparatus is 

 clearly traced, that the conveyance of aliment to 

 the organs is most satisfactorily observed ; and they 

 seem to have been unable to conceive any other 

 mode by which this purpose could be effected. But, 

 when we attend to some organs, particularly hair 

 and feathers, we find them too dry to admit the 

 supposition that fluids are circulated through every 

 part of their substance. Physiologists must always 

 have supposed that, in these organs, the propor- 

 tion of the fluid to the solid matter is much smaller 

 than in the muscular and nervous substance ; but 

 they have not supposed that there was any limit to 

 the tenuity of vessels by which fluids are conveyed. 

 This view is sometimes applied to the physiology of 

 the smallest insects. They are described as possessed 

 of vessels equally numerous as in larger animals, 

 and carrying to every organ the nutritious fluid in 

 streams which obey the same vital and hydraulic 

 laws. 



We shall, find, however, that, in the laws of ca- 

 pillary attraction, limits are set to the tenuity of 

 sanguiferous vessels. In consequence of these laws, 

 a small portion of the area of the contained fluid 



