342 ANIMAL HEAT. 



should, as a rule, be a little higher than that of the surround- 

 ing atmosphere. Not only is this the condition most favour- 

 able to the accuracy of the observations, but it is most advan- 

 tageous as regards the state of the animal observed. If the 

 temperature is too high, the disengagement of heat from the 

 surface is relatively lessened, so that unless completely com- 

 pensated for by increased evaporation, the bodily temperature 

 of the animal will rise. If, on the other hand, the tempera- 

 ture of the calorimeter is lower than that of the surrounding 

 air, that of the animal sinks so quickly that its condition is 

 no longer normal. It is obviously of great importance that 

 the observations should be made in a room of even tempera- 

 ture, and it is desirable that it should not be too cold. 



The method above described may be applied not only to the 

 investigation of periodical and other physiological variations 

 of the process of nutrition, but to the investigation of many 

 abnormal states and alterations, such for example as those of 

 fever changes affecting the condition of the surface of the 

 body, changes affecting the circulation, respiration or nervous 

 system, and changes produced by the action of various drugs. 1 

 -,-For the investigation of fever, the pyrexial state ma}' be pro- 

 duced experimentally, either by injecting into the venous S3 T s- 

 tem small quantities (5 to 15 minims) of the exudation liquids 

 of certain acute inflammations ; or by producing a local in- 

 flammation, e.. j;., by applying croton oil to the surface. Al- 

 though the increase of temperature produced by these methods 

 has been carefully investigated by the thermometer, no suffi- 

 cient investigations have as yet been made as to the quantity 

 of heat produced in a given time. Among other subjects 

 which admit of calorimetrical investigation, that of the remark- 

 able effects produced in rabbits by the process of " varnish- 

 ing" may be referred to. 



117. Increased Discharge of Heat of "Varnished" 

 Rabbits. It is well known that rabbits when smeared over 

 the clipped surface with gelatin or any other similar material, 



1 Considering that it is not possible, even with the utmost care, to 

 keep the animal in a perfectly natural condition during a calorimetrical 

 observation, and that there are certain sources of error inseparable from 

 the method itself, which do not admit of being corrected for, it is advi- 

 sable in employing the calorimeter for physiological investigations to 

 estimate the value of the results obtained not by calculation but by 

 comparative experiments, e. g., (1) by comparing the result obtained 

 under the condition to be investigated with the result obtained in the 

 normal state of the same animal ; (2) by employing in each observation 

 two calorimeters, in one of which the animal is placed, while the other 

 remains unoccupied, but in all other respects under the same conditions. 

 In this case, the loss of heat, if any, during the period of observation 

 in the empty calorimeter is to be added to the gain in the one in which 

 the animal is contained. 



