34 IMPORTANCE OF CAPILLARY ATTRACTION IN PHYSIOLOGY. 



laboratory assimilating things for its own substance. The simplest plants, confervae, 

 tremellse, and the simplest animals, consist alone of this structure. Let us observe 

 how nearly this vesicle agrees, both in its constitution and mode of action, with the 

 vesicle of (80). Like that, it is not only an imperforate cell, but also consists of simi- 

 lar elements. The properties which the organized vesicle is supposed to enjoy are 

 met with in the fullest extent in that which is not organized. Both have powers of 

 endosmosis, and a species of assimilation of things exterior to their own substance. 

 What property has the lowest order of animal and vegetable life which that bubble 

 does not possess ? A thing thus endowed with vitality may well excite our interest ; 

 it breathes, it is nourished, it exhales. 



105. By referring the phenomenon of endosmosis to absorption, such as has been 

 recognised by chemists, we advance one point in the simplification of our knowledge. 

 It gives us also a better idea of the specific action of tissues, as depending on structural 

 arrangement, and presents an intricate problem in its easiest form for solution ; more- 

 over, it is, as I know by experience, a safe guide in experimental research. We can 

 hardly doubt that the forces bringing about the result indicated in (80) are the same as 

 those which operate in Dr. Mitchell's experiment, where India-rubber is used as a bar- 

 rier; and if that result receives so ample and so easy an explanation upon this doc- 

 trine, why should we hesitate to apply it to the other? But the composition, structure, 

 and habitudes of a thin, watery film, are much better known than those of a lamina of 

 India-rubber : we can reason with certainty respecting the one, and vary its composi- 

 tion to suit the purposes of experiment ; the other affords no such advantage. If, how- 

 ever, it should eventually be found that the simple doctrine of absorption is not suffi- 

 cient to explain all the phenomena of endosmosis that may hereafter be discovered, this 

 paper will at least prove that the cause of those phenomena is not alone enjoyed by 

 organic and solid tissues, but also by liquids and substances without organization. 



CHAPTER V. 



THE PHYSICAL THEORY OP CAPILLARY ATTRACTION. 



(From the American Journal of the Medical Sciences for February, 1838.) 



CONTENTS : Importance, of Capillary Attraction in Physiology. Capillary Attraction 

 is an Electrical Phenomenon. Its Physical Theory. The Effect varies ivith Varia- 

 tions of Electric Disturbance. Takes place between Bodies of different Forms. 

 Physiological Illustrations. 



106. IT has been alleged, as a bar to all physiological investigation, that the phenom- 

 ena of life are of so peculiar a nature, that we must necessarily forever remain ignorant 

 of their causes ; that, unlike physical phenomena, which are of a simpler kind, and more 

 within the reach of human understanding, there is something in these inherently myste- 



