294 Medicine. [Chap. IV. 



through its moistened coats, by the florid colour 

 thence imparted to the blood, in order to demon- ^ 

 strate the mode m which oxygen fmds its way 

 through the coats of the blood-vessels in the lungs. 



Dr. Goodwin was the author of the celebrated 

 experiment, in which the action of the lungs is ex- 

 hibited by opening the chest of a living dog, and 

 exposing to view the motion of the lungs and heart* 

 In this experiment, the blood driven from the right 

 ventricle of the heart into the pulmonary artery 

 appears of a dark venous complexion ; but on its 

 return from the lungs, by the pulmonary veins, it is 

 changed to a bright vemiilion colour. He also de- 

 monstrated that the bright florid appearance of the 

 blood, derived from oxygen received in the lungs, 

 is absolutely necessary to enable it to stimulate 

 the left ventricle of the heart, in order to produce 

 the contraction which propels the blood into the 

 aorta. For whenever an intermission in the mo- 

 tion of the lungs denied the access of air, the blood 

 in the pulmonary veins returning to the heart was 

 of a dark purple colour, and was no longer sufli- 

 cient to excite the due contraction of that organ. 



That respiration is the source of the temperature 

 of animals, or of what is commonly called animal 

 heat, is one of the results of the light recently 

 thrown on that function. Physiologists long ago 

 observed that animals which do not breathe have 

 a temperature little higher than the medium in 

 which they live. This is the case with flshes and 

 many insects. Man, quadrupeds, and birds, on 

 the contrary, have a temperature considerably 

 higher than the ordinary states of the atmosphere. 

 It may hv i)rovcd f hat the heat of all animals is pro- 



