352 Thermal Adjustment and Respiratory Exchange. 



exhibits very marked hysteresis with respect to H and B. Over a part 

 of the cyclic h-B curve, the direction of h is opposite to that correspond- 

 ing to the direction of the induction at the centre of the wire. The 

 results obtained show that the method of " shearing" usually adopted 

 to correct B-H curves for the effects of the de-magnetising force must 

 be used with great caution. 



The paper is illustrated by diagrams of apparatus and by curves 

 showing the experimental results. 



" Thermal Adjustment and Eespiratory Exchange in Monotr ernes 

 and Marsupials. — A Study in the Development of Homo- 

 thermisin." By C. J. Martin, M.B., D.Sc., Acting Professor 

 of Physiology in the University of Melbourne. Communi- 

 cated by E. H. Starling, F.B.S. Keceivecl May 14, — Eead 

 June 6, 1901. 



(Abstract.) 



A number of observations on the relations between the body tem- 

 perature, and the temperature of the surrounding medium, and on the 

 respiratory exchanges m monotremes and marsupials are recorded. 

 The results are compared with those obtained in control experiments 

 with cold-blooded animals (lizards) and higher mammals. 



The main conclusions arrived at are — 



1. Echidna is the lowest in the scale of warm-blooded animals. Its 

 attempts at homothermism fail to the extent of 10° when the environ- 

 ment varies from 5° to 35° C. During the cold weather, it hibernates 

 for four months, and at this time its temperature is only a few tenths 

 of a degree above that of its surroundings. The production of heat in 

 Echidna is proportional to the difference in temperature between 

 animal and environment. At high temperatures, it does not increase 

 the number and depth of its respirations. It possesses no sweat glands, 

 and exhibits no evidence of varying loss of heat by vaso-motor adjust- 

 ment of superficial vessels in response to external temperature. 



2. Ornithorhyncus is a "distinct advance upon. Echidna. Its body 

 temperature though low is fairly constant. It possesses abundant 

 sweat glands upon the snout and frill, but none elsewhere. The pro- 

 duction of carbonic acid with varying temperatures of environment 

 indicates that the animal can modify heat-loss as well as heat-produc- 

 tion. Its respiratory efforts do not increase with high temperatures. 



3. Marsupials show evidence of utilising variations in loss to an extent 

 greater than Ornithorhyncus, but less than higher mammals. Their 

 respirations slightly increase in number at high temperatures. 



