110 PROCEEDINGS OF THE ACADEMY OF [March, 



From these experiments we see, that respiration must be carried 

 on by one of two methods — (1) by the rectum or (2) through the 

 integument. The probability of the passage of the air of the water, 

 through the chitin of the body is quite doubtful. The larvae used 

 were for the most part of rather hard, thick chitin and the passage 

 of the air through this would be very slow and in all likelihood 

 too small in amount to serve the entire respiratory needs of the 

 larvae. The possibility of the larvae getting near or on the surface 

 of the water and taking in air through the spiracles present on the 

 thorax or directly through the skin is excluded, since the larvae 

 could not get to the surface. The only method left, by which the 

 air could have been taken in, was by means of the rectum. The 

 manner in which the air is taken out of the water by the larval 

 rectum is one of dispute and need not be taken up here. Tillyard 

 (1915) has admirably discussed this question and reference to his 

 work Avill show the present views. 



In experiments made with other objects in view, viz., the action 

 of certain gases or fumes of chfferent chemicals, e. g., ether, chloro- 

 form, etc., upon the heart's action, verj^ interesting phenomena 

 were observed with respect to their effects upon the contractions 

 of the rectum. The details of these experiments will not be given 

 now, but their effects on the respiratory phenomena in which we 

 are interested will be considered. 



Before the various gases affect the action of the heart, violent 

 contractions of the rectum always precede and very shortly afterward 

 the effects upon the heart's action can be observed. In an animal 

 which has been under the influence of the gas and is recovering, 

 similar contractions of the rectum can be observed before the heart 

 again beats normally. These observations would seem to show 

 that the gas is first taken into the rectum and distributed from it 

 to the other parts of the body. The contractions, when the animal 

 is recovering, would also seem to indicate that air must be carried 

 to the tissues before normal activities could again be resumed. 



If the larvae breathe through the skin, these contractions of 

 the rectum would be quite superfluous. They cannot be due to the 

 action of the gas used, as when the larva was recovering, it was kept 

 in normal atmosphere, away from the effects of the gas. Hence 

 the rectum must in some way act as a respiratory center for the 

 larvae. 



The distribution of the tracheae, and the general structure of the 

 rectum of the larvae employed in these experiments correspond 



