792 REPORT— 1894. 



the developing chick is exposed to shock by the prolonged action of cold, this 

 neutral condition may be replaced by a return to the cold-blooded stage. 



The reaction of the recently-hatched chick is rapid ; a fall of 20° in tempera- 

 ture will within fifteen minutes raise the carbonic acid to double its previous 

 amount. 



It would appear that this power of regulation depends upon the integrity and 

 full development of the nervous control of muscular action. The chick directly it 

 is hatched possesses great control over its muscles ; it is able to run about, feed 

 itself, and perform other complicated movements. At the same time it is able to 

 regulate its production of heat. 



It was probable that animals born blind and in a very helpless condition would 

 not possess this power of regulation ; that in their case a fall in external tempera- 

 ture would be accompanied by a decrease in carbonic acid, and that with a rise of 

 temperature the output of carbonic acid would be increased. This has been proved 

 to be true in the case of the pigeon. A young pigeon was examined, when it was 

 one day old, and it was found that a fall of 14° in external temperature caused the 

 carbonic acid to diminish to one-third its former value within thirty minutes of the 

 change in temperature. When two days old a similar change of temperature pro- 

 duced almost as great a fall in the output of carbonic acid ; raising the temperature 

 to its former level did not cause the carbonic acid to Increase with the same rapidity 

 with which it had fallen. 



Thus a young pigeon resembles to a certain extent a cold-blooded animal. 

 There is, however, one great difference. The young pigeon responds very rapidly, 

 the frog responds extremely slowly. 



To study still further the influence of the nervo-muscular system upon the 

 regulation of temperature by the production of heat, experiments have been made 

 upon mice after section of the spinal cord and during anaesthesia. Both these 

 procedures tend to make the mouse respond in a somewhat similar way to that 

 observed in the cold-blooded animal. 



The writer has to thank Messrs. Gordon and Warren for much assistance ini 

 some of the experiments. 



2. On some Experiments to deterviine the Time-relations of the Voluntary 

 Tetanus in Man} By David Fraser Harris, B.Sc. Lond., M.B. 



1. In a large number of experiments the following apparatus was used : — 



A metallic case, made air-tight at each end, was fitted over the forearm from 

 below the elbow to near the wrist. This instrument, practically an air-plethysmo- 

 graph (for it could register the pulse-beats), had a circular aperture cut in the upper 

 surface, and over this space was fastened a membrane of gold-beater's skin, to which 

 was fastened a disc of platinum. There was no tension exerted on the membrane, 

 which the slightest increase of pressure caused to move, but which, on the cessa- 

 tion of the agitation, came immediately to rest. 



Touching the platinum disc was a fine metallic point — the end of a screw sup- 

 ported by an upright soldered to the metallic case. A wire was led to a battery, 

 thence the current traversed an electro-magnetic writer (or ' signal '), and the cir- 

 cuit was completed to the screw-point. The vibrations of the muscles of the fore- 

 arm thrown into voluntary tetanus {via the air under the membrane) agitated the 

 membrane, and so made and broke the current, these interruptions in turn synchro- 

 nously affecting the writing style of the electro-magnet, which traced on a 

 revolving drum a myogram of ' incomplete ' tetanus. The rhythm of this as com- 

 puted from nine different parts of a tracing varied thus : 10, 12, 23-3, 10, 10, 20, 20, 

 20, 26 "6 vibrations per second, or on an average 168. The average of a very 

 large number of computations was 133. 



2. The method employed by Schafer- gave exactly similar results — viz. an 

 average of 10, 8 to 13 being the minimum and maximum rates respectively. 



' The paper is published in the Journal of Phjswlogtj, October 1894. 

 ^ Journal of Physiology, vol. vii. 



