122 ANATOMY AND PHYSIOLOGY. 



tion of the phenomena of animal heat that we at present possess. 

 One modification of this theory we may here state. It has been 

 supposed that the oxygen, when it is absorbed by the blood in the 

 lungs, exists there only in a loose state of combination ; that as it 

 circulates, the union with the carbon, &c., of the blood, becomes 

 more intimate ; and that the heat comes thus to be gradually dis- 

 engaged, and diffused through every part of the body. For further 

 information on this subject we must refer to the works of Drs. Smith, 

 Alison, Bostock, &c. ; but we must not omit to mention that many 

 facts, which our limits will not allow us to state, prove decisively that 

 the nervous system is connected, directly or indirectly, with the pro- 

 duction of animal heat. We can only state generally, also, that 

 the body possesses the power of keeping down its heat to nearly 

 the natural standard, even when exposed to a very high tempera- 

 ture. Sir Charles Blagden remained, without any great incon- 

 venience, in a room, the temperature of which was fifty -two degrees 

 above that of boiling water, until eggs were roasted hard, and a 

 beefsteak made ready by blowing air on it.* Indeed, the heat of 

 his body, though the temperature of the apartment was 264 degrees^ 

 rose only three or four degrees above ninety-eight degrees, its 

 natural standard. It has been found that the principal agent in 

 keeping down the temperature, is the immense evaporation that 

 takes place from the lungs and skin. Accordingly when the skin 

 is varnished, or the air of the apartment is saturated with moisture, 

 so as to prevent evaporation, a temperature one-half so high can 

 hardly be borne. 



Having now given a short but connected account of the physi- 

 ology of respiration, we cannot but remark how varied arid how 

 complicated are the agents employed, and yet how accurately each 

 of these performs the part assigned it. Such investigations as those 

 with which we have been occupied, form the proper foundations of 

 natural religion. No one can rise from the study of these parts of 

 the animal frame, without intensely feeling that design, and design 

 of a kind the most exquisite, guides every motion and change of 

 the vital fluid. Never did any piece of machinery invented by 

 man, indicate with greater precision the intentions of its maker. 



The voice is produced in what is called the larynx, at the top of 



the windpipe. The air, in passing through its opening (glottis), 



causes parts called vocal ligaments to vibrate, and to give out the 



different varieties of sound. These sounds can be further modified 



* Dr. Chaubert, of this city, a few years ago practised the same experiment. 



I 



