45^ An Account of some Experiments on Animal Heat. 



of the parts from tiie heart increases — are the general results of 

 the preceding espcriments. 



Admitting the accuracv of these experiments, and I think that 

 tlicy will l)c found correct r.hcn repeated, wiiat are their conse- 

 quences in a theoretical poiiu. of view ? 



They arc evidently in direct opposition io Dr. Crawford's 

 hypothesis ; the essence of which is, that the capacity of arterial 

 blood for heat is greater than that of venous, that there is no 

 difference of temperature between the twb ventricles of the heart, 

 and iu fact that the heat of all parts is nearly the same. 



They are more agreealile to, and indeed they ev^-n support, the 

 hypothesis of Dr. Black, that animal heat is produced in the 

 lungs, and distributed over the whole system by means of the 

 arterial blood. 



Neither are they inconsistent with that hypothesis which con- 

 siders the production of animal heat as dependent on the energy 

 of the nervous system, and arising from all the vital actions con- 

 stantly occurring. 



Besides the results of the preceding ex|)eriment«;, many argu- 

 ments may be advanced in opposition to Dr. Cra\vford's hypo- 

 thesis. 



As we never perceive a difference of capacity in bodies with- 

 out a difference of form or composition ; and as very slight dif- 

 ferences of the former result only from great changes of the latter; 

 it might be expected a priori, as no difference, excepting tliat 

 of colour, has been detecte*} between venous and arterial blood, 

 that their specific caloric would be very similar. Fr. m analogy 

 also, it might have been expected, that tlie capacity of arterial 

 blood for heat would be much less than that of water, as water 

 appears to exceed almost every other fluid, and as the capacity 

 appears to diminish as the infiammabilitv of compounds increases. 

 But the strongest argmiieuts against this hypothesis are to be 

 derived from the recent experiments of Mr. Brudie, and those 

 of iMM. Delaroehe and Berurd. 



Dr. Black's hypothesis appears to me far more satisfactory 

 than Dr. Crawford's, and capable of explaining a much greater 

 number of phfpuomena ; but there are objections even to this 

 hypothesis, which must be removed before it can witli propriety 

 be received. 



The last hypothesis, wliich I mentioned, that which refers 

 animal heat to vital action, has irxany facts in its support, arid 

 especially the results of Mr. Brodie's ciu'ious and interesting ex- 

 perimoifs ; and the results of my inquiry, as I have already ob- 

 served, arc not incompatible vdth it. It may be said, that the 

 viscera of the tiiorax and abilomen are of highest temperature, 

 because these parts arc, as it were, the elaboratories of life •■, and 



that 



