204 



Mr. J. M. O'Connor. 



and the carbon dioxide never rose above 1 per cent. The airtightness of the 

 apparatus without disconnecting the animal was tested after each experiment. 



If in an experiment the beginning of which I have described the animal be 

 left exposed to the room temperature or put in a bath of say 25° C. it shivers 

 violently. This shivering can be seen in the animal without any artificial 

 respiration, but under the conditions of the experiment, provided the ventila- 

 tion be efficient, is much more pronounced. It is especially marked during 

 the down strokes of the pump. If the temperature of the bath be now 

 gradually raised, the temperatures of the subcutaneous tissue and rectum 

 gradually follow and the shivering becomes noticeably less. The oxygen 

 consumption plotted against the average rectal temperature for these periods 

 gives no constant relation. "When, however, the temperatures have risen 

 above a certain point — always less than the normal temperature of the animal 

 — shivering stops completely, and from this point on the oxgyen consumption 

 is within limits directly proportional to the rectal temperature, just as it is in 

 the cold-blooded animal (Schultz, 17). If now this line be extrapolated into 

 the region in which the animal was shivering and the figures obtained be 

 deducted — they are always less — from the observed consumption of oxygen 

 at various rectal temperatures, the difference plotted against the corresponding 

 average skin temperatures gives approximately a straight line. In other 

 words the " extra O2 " consumed during shivering is proportional to the extent 

 to which the subcutaneous temperature has fallen below a fixed point. 



The gradient of this extrapolated line varies in different animals. It tends 

 to cut the abscissa at a point between about 19° and 29°, resembling the steep 

 portion of Schultz's curve (see C. S. Martin, 18). 



Fig. 2 gives as an example one of many experiments done. Considering 

 the necessary inaccuracies of the observations all accumulating in the final 

 result, the regularity — apart from three outstanding figures — is sufficiently 

 striking. 



The lowering of the skin temperature therefore produces an activity of the 

 muscles which is accompanied by, or we may say without prejudice results 

 from, muscular activity. This muscular activity as indicated usually takes 

 the form of a fine incoordinate shiver ; but it is not always so. Occasionally 

 in the rabbit the shivering is interrupted by periods of running movements 

 similar to those seen in chloroform narcosis without an obvious alteration in 

 the O2 consumption. In extreme cold convulsive movements may occur, and 

 frequently there is in addition to the shiver a tonic cramp-like rigidity, easily 

 noticeable on palpation. The fall of skin temperature appears consequently 

 to result in a demand for a certain amount of activity from the muscles, which 

 presumably in the absence of other directive impulses takes the form of a 



