200 CARNEGIE INSTITUTION OF WASHINGTON. 



The remaining experiments on the response to changes in temperature 

 were carried out to obtain a comparison of the response to changes of tem- 

 perature of the two halves of a disk, one of which retained its sense-organs, 

 while the other was activated by a circuit wave of contraction. As a general 

 statement of the results, not all the data of which have as yet been reduced 

 to graphic form, it may be said that for an increase of 10° C. from 23° to 

 33° the pulsation-rate of the activated disk was approximately doubled. 

 Beyond a temperature of 35° there was a rapid decline in the rate, pulsation 

 ceasing at about 40°. The curve for this increase was up to 35° a right 

 line, not a logarithmic curve, as would be true for a purely chemical reaction. 



The rate for the half-disk with sense-organs reached its maximum from 

 27° to 29° and then slowly declined until pulsation ceased at about 40°. 

 These specimens, if cooled slowly, took up pulsation again at about 37°, 

 and in several instances were kept alive for a number of days after the 

 experiment. The change in rate was often very erratic in specimens with 

 sense-organs, and the maxima varied from 1.3 to 6 times the original rate. 



E. The Relation Between the Area of Tissue Ennervated by a Single Sense- 

 Organ and the Rate of Pulsation. 



The study of a large series of disks under the control of a single sense- 

 organ has shown that there is a regular decline in the rate of pulsation as 

 the tissue area is reduced until when the area is one-sixteenth that of the 

 original area the rate of pulsation is one-half that of the entire disk.^ This 

 research was continued during the present season in the hope of securing 

 some evidence as to the nature of the factors determining this reduction 

 in the rate of pulsation. It was found that when the area of tissue was 

 reduced to f I g of the original size the muscles and nerves were still capable 

 of responding to induction shocks at the rate of 120 per minute. There is, 

 then, apparently no need for a latent period on the part of the muscle-tissue. 

 When the area of the muscle-tissue under the control of the single sense- 

 organ was reduced by putting a part of it into 0.4 m. MgCla the rate of pulsa- 

 tion was reduced to the same extent as when an equal amount of tissue was 

 removed by severing the muscles and nerves. This was true when the 

 anesthetized tissue was in the middle of the strip as well as when it was at 

 the end opposite to the sense-organ. 



This result would indicate that the area of active muscle was the determin- 

 ing factor since the nerves were still capable of transmitting the stimulus for 

 contraction as is shown when the narcotized area is in the middle of the strip 

 of tissue. 



Experiment on the Feralization of the Albino Rat, by Henry H. Donaldson. 



In relation to the body-weight, the brain of the albino rat is about 12 per 

 cent lighter than that of the wild Norway rat, from which this albino has 

 been derived. 



There was some reason to think that this character of the albino was due 

 to the influence of domestication, and I wished therefore to establish a colony 

 of these animals under conditions which would permit them to live in a wild 

 state, in order to determine whether the relative weight of the brain would 

 in successive generations return to that characteristic for the wild Norway. 



In June 1914 Dr. Mayer placed on East Key in the Tortugas, Florida, 

 8 albinos (4 males and 4 females) which were sent from Wistar Institute. 

 The rats were about 90 days old when released, but unfortunately were not 

 ear-marked. 



'Gary, L. R., Year Book No. 14, Carnegie Institution of Washington. 



