4 Olservations relating to the Connexion letween vascular 



pretension to dive into the hidden mystery of vitality, confessing 

 myself wholly incompetent to reduce that power within the rules 

 of physical science: a power which appears to my judgement as 

 allied to the nature of an inscrutable First Cause or an emana- 

 tion from it. 



The vast variety in substances, textures, bulk, and combi- 

 nations, which the living animal and vegetable kingdoms ex- 

 hibit, render it difficult to define the essential residence of life 

 as connected with any of the modes of organic structure. Some 

 of the compounds and textures of animals are known to be more 

 important for the maintenance of life than otiiers ; as the cerebral 

 suljstance and the muscular textures : but there is a numerous 

 tribe of liviug bodies that appear to be wholly destitute of those 

 peculiar parts ; of which the entire vegetable kingdom may be 

 adduced as an instance. Habits of meditation and research have 

 led me to conclude, that some benefit may arise to physiology 

 from more accurate discriminations between the several sub- 

 stances of living bodies, especially as to the relative dominion of 

 vitality or physical causes oa those substances respectively. 



The active phajnomena of life appear to be generally distinct 

 from those of physical causation, but the passi\e condition of 

 living substances is not so obvious. The suspended action of 

 torpid animals and vegetables, and the latent vitality of many 

 of the more simply constructed animals and vegetables during 

 the absence of heat and moisture, show the intimate connexions 

 which subsist between vitality and physical causes. Difficult and 

 intricate as these investigations may seem when extended to all 

 the cases of vita! phsenoinena, they are not so in the grosser ex- 

 aniples to be now adduced; and if it should be found that many 

 substances distinctly continuous with vital organic bodies are 

 wholly subjected to physical dominion, and tluit several other 

 substances are in part influenced by the one cause and by the 

 other, it m,ay perhaps o])en new and more precise views in the 

 medical art. Those parts of organic bodies which have no 

 power of self-repair, which hold no continuity with the circula- 

 ting fluid material destined to replenish the waste, to augment 

 the bulk, or repair the accidents of the living fabric, may be 

 justly deemed extra-vital. The exuvial defences or coverings of 

 animals are of this kind ; namely, hairs, nails, feathers, and all 

 cuticular structures, as v.ell as the epidermoid coverings and 

 husks of the vegetable kingdom : some of those substances which 

 are destined to be worn away, retain a partial continuity with 

 the organic system of circulating fluids, as the growing bulbs of 

 hairs, the roots a?id laminae of nails and hoofs ; whilst other parts 

 which are destined to be shed, as feathers and cuticular scales, 

 are wholly detached from the vascular communion after their 



comj)lete 



