30 LIFE. 



life ; and one may more easily believe it to have been alive in 

 the mass of blood, than that it should have acquired vitality after 

 its effusion. Indeed Sir Everard Home declares that a coagulum 

 of blood becomes vascular out of the body, and may be injected ; 

 but if the vessels are formed by the mere extrication of carbonic 

 acid gas, as he contends, their mere formation is no proof of life. 



John Hunter believes that the chyle is alive, and some that 

 vivification commences in the stomach ; and Albinus grants life 

 even to the excrement. But the excretions must be regarded 

 as dead matter, useless and foreign to the system, and they all 

 run with the greatest rapidity into decomposition. In operating 

 for retention of urine, the surgeon finds this fluid abominably 

 foetid; the faeces become so when not discharged in due time; 

 and the neglect of washing the surface is the source of filth and 

 disease. 



The essential nature of life is an impenetrable mystery, and no 

 more a subject for philosophical enquiry than the essential nature 

 of attraction or of heat. To attempt explaining the phenomena 

 of life by a vital fluid is only increasing the intricacy of the 

 subject by an unfounded hypothesis, and always reminds me of 

 Mr. Dugald Stewart's remark, " That there is even some reason 

 for doubting, from the crude speculations on medical and chemical 

 subjects which are daily offered to the public, whether it (the 

 proper mode of studying nature) be yet understood so completely 

 as is commonly imagined, and whether a fuller illustration of the 

 rules of philosophising, than Bacon or his followers have given, 

 might not be useful even to physical enquirers." p We see matter 

 in a certain state possessed of a certain power which we term life, 

 and the object of physiology is merely to observe its effects, just 

 as it is the object of chemistry to observe the circumstances of 

 the affinity of different bodies and of physics to observe other 

 phenomena of matter, without vainly speculating on the essence 

 of affinity or the essence of matter, to comprehend which our 

 faculties are, in their nature, incompetent. By attributing life, 

 the power of attraction, &c. to subtle and mobile fluids, we not 

 only do not advance a single step, for we have still to explain 

 what these fluids are, and how they obtain their powers, just as we 

 had before in regard to common matter ; but we make the addi- 



Phil. Trans, vol. cviii. p. 188. sq. 



p Elements of the Philosophy of the Human Mind, vol. i. p. 8. 



