ON THE ANIMAL FRAME. 293 



has ever been given ; yet it must be allowed to 

 be one of importance, both as it affects the phy- 

 siology of the Animal and Vegetable kingdoms. 



Having had occasion for a few weeks past to 

 ruminate on this subject, some new views have 

 occurred to me ; and it is the object of the pre- 

 sent essay to unfold them, in order to elucidate 

 the phenomena arising from aerial pressure on 

 the animal economy more especially. 



It is pretty well known that the specific gra- 

 vity of living men in general, is less than that of 

 water.* Mr. Ro]>ertson, formerly librarian to 

 the Royal Society, procured an apparatus for the 

 purpose of determining the specific gravity of 

 the human body. He chose ten men promiscu- 

 ously for the purpose. Of these, three were found 

 very nearly of the same weight as water, one 

 being a little heavier, and the other two a little 

 lighter than water : two others were found only 

 about .8 the weight of water ; but the other five 

 were of intermediate specific gravities. The ave- 

 rage of the ten was — height, 5ft. 6f ins. — weight, 

 146lbs — specific gravity, .891 — bulk, 2.618 cubic 

 feet. From this I think we may safely infer that 

 the body of a full grown living man, when plunged 



• Phil. Trans, vol. 50.— Mutton's Diet. Sp. Gr. 



