106 ANIMAL HEAT. 



tern. Finding afterwards that the consequences which 

 you suggested rendered this theory untenable, they con- 

 cluded at last that the oxygen was absorbed into the ves 

 sels, and that its combination with carbon, and the con- 

 sequent disengagement of heat, took place gradually 

 throughout the whole venous system. Thus a constant 

 and equal warmth is diffused over the whole body. 



Emily. What a beautiful theory ! How admirably 

 the greatest results are sometimes effected by apparent- 

 ly the most ordinary agents. 



Dr. 13. Beautiful indeed it is ; but unhappily we 

 cannot speak so favorably of its truth. The venous 

 blood in which the carbonic acid is supposed to be form- 

 ed, instead of indicating; a higher temperature than the 

 arterial blood, as it evidently ought, is even two or three 

 degrees lower. This, together with many other facts 

 which have been established by later experiments, have 

 now pretty generally discredited the theory, and Physi- 

 ologists have been obliged to turn their attention to 

 some other source for an explanation of the effect ia 

 question. 



Emily. If the same theory was expected to apply 

 to the respiration of plants, it must inevitably have been 

 falsified there. Plants have a temperature above that 

 of the atmosphere in the middle of winter. I have of- 

 ten observed that the snow which falls on their limbs 

 and around their roots, soon melts away, and Dr. S. 

 mentioned last summer in his botanical lectures, that if 

 the bulb of a thermometer be introduced into the trunk 

 of a tree in the coldest day, the mercury will rise above 

 the freezing point. At this time their branches are des- 

 titute of foliage and no respiration can consequently be 

 going on. 



Dr. B. We are not positive that vegetable heat and 

 animal heat are both produced in the same way ; but 

 still if you had been sufficiently acquainted with the 

 subject, you might have adduced analogies from the an- 

 imal kingdom, equally conclusive. Many reptiles lie in 



