422 EESEARCHES UPON FEVEE. 



the surplus caloric of tlie body has been yielded up, and tiien becomes 

 proportionate to the diminished heat production. 



The cause of the primary increased heat evolution is probably vasomo- 

 tor palsy. The interior of the body maintains its temperature by keep- 

 ing a partially cooled layer between it and the external air. When the 

 external cold is great, the superficial vessels are contracted, and loss of 

 heat is as far as possible prevented. After section of the cord, the super- 

 ficial capillaries relax and the surface temperature rises. Later on, as 

 the interior heat fails, the superficies and the deep parts of the body 

 alike grow cooler, and the great loss of heat is arrested. A question 

 now lU'csented itself for solution, as to how far the loss of heat directly 

 checks chemical movements inside of the body, and how far the lessened 

 heat production after cord section is the direct result of such influence 

 of the cold. This was partially solved by i)lacing the animal in a calo- 

 rimeter heated to about 100° Fahr. Under these circumstances it was 

 found that sometimes the heat production was maintained after the 

 operation, but in other cases was markedly diminished : the causes of the 

 diiference will be fully detailed in the extended memoir, but are here 

 omitted. The calorimeter worked at a high temperature is not an 

 instrument of precision, so that no absolute authority can be accorded 

 to the experiments just spoken of. Nevertheless it will be seen that the 

 i-esults accord with the fact (earlier stated) that sometimes in the heated 

 chamber rise of the bodily temperature was more pronounced after than 

 before section of the cord. The evidence indicates that after spinal sec- 

 tion the diminished heat production is not always or even usually in chief 

 part caused by loss of heat, but that the reduction of temperature may 

 have some influence in lessening the activity of the chemical movements 

 of the body. 



When the great rise of bodily temperature that follows immediately 

 section of the cord above the governing vasomotor center in the medulla 

 is called to mind, the necessity of studying as to whether this rise is 

 due to disturbance of heat evolution or heat production becomes appa- 

 rent. Such studies reached the result that heat production is excess- 

 ively increased by section of the cord at its junction with the pons. 



An elaborate series of experiments were performed confirming the results 

 l)reviously reached by other observers, that if changes in the arterial pres- 

 sure can be taken as a guide, the governing vasomotor center is situated 

 in the medulla oblongata. Conceding this, it would seem i^roven that 

 vasomotor paralysis is the cause of the diminished heat production which 

 usually follows section of the dorsal spinal cord, even when the bodily 

 temperature is artificially maintained. It is plain how such palsy must 

 everywhere render the circulation much less quick, more sluggish than 

 normal, and this is i^robably the immediate cause of the failure of heat 

 productions. The fact that sometimes, especially in very vigorous dogs, 

 the production of heat was rather increased than lessened by spinal 

 section, indicates that there is some influence at work antagonistic to 



