182 



authority of Cuvier it has been objected that intiapulmonary 

 bronchial cartilages are absent in certain other mammals such as 

 Herpestes and Mycetes (6). The original statement is inaccessible 

 to me in Cleveland. I have not been able to obtain a specimen of 

 Mycetes. But examination of serial sections of the lung of Her- 

 pestes shows that for this animal at any rate the statement is inaccu- 

 rate. It is possible to obtain a slide showing absence of cartilage in 

 an intra pulmonary bronchus. But if 2 or 3 serial sections be taken, 

 it is plain that cartilage is present as in other mammals. 



It is stated by Gegenbaur that the intrapulmonary bronchial 

 cartilages are poorly developed in some Marsupials, Prosimidae and 

 Chiroptera and are altogether absent in certain apes (Mycetes) (11). 

 Possibly in these last-named animals, different respiratory conditions 

 have lead to the same result which is found in the elephants i. e. 

 absence of intrapulmonary bronchial cartilages. 



In conclusion I would offer my grateful acknowledgment to 

 Messrs. Jennison for the opportunity afforded to make these obser- 

 vations and to Messrs. Lawrence, Stansfield and Gosling, keepers 

 in charge of the elephants for much patient help in the clinical in- 

 vestigation. I would also express my indebtedness to Mr. H. Goo- 

 ding of the Anatomical Department University of Manchester for 

 carrying out the histological technique, and to Mr. J. C. Miller of 

 the Anatomical Department Cleveland for his assistance in abstrac- 

 ting the literature. 



Summary. 



1. The pleural cavity is absent in elephants, not as a pathological 

 condition, but as the normal occurrence. 



2. Contrary to the usual mode of respiration in Ungulata, the 

 elephant breathes mainly as a result of diaphragmatic, and not of 

 costal movement. 



3. The absence of pleural cavity in the elephants is associated 

 with absence of intra-pulmonary bronchial cartilages. 



4. Both of these conditions may be related to the modification 

 of respiration rendered necessary by the presence of a proboscis. 



