478 Mr. L. Hill. The Influence of Tncreasecl Atmospheric 



. Although no sound dassification can be based on one single organ, a 

 striking concordance exists between an attempted arrangement of the 

 Mammalia according to the Fundus oculi and the most modern classifi- 

 cation. The cases of disagreement are wonderfully few. These are 

 restricted to the following : — 



Chrysothrix leans towards the Arctopitheci. I find it necessary to 

 separate the Galagos from the rest of the Lemurs — at least, as a sub- 

 family. In the smaller Carnivores it is advisable to establish a separate 

 family, the Cf/nicfida\ to include the other^^dse ^iverrine genera, Cynictis 

 and Galictis, together T^^th ]^Iephitis, hitherto placed with the Mus- 

 telida3. The Sciuromorpha should be divided into Sciuridae and Ptero- 

 myidge, and Castor should decidedly be removed into the Hystricomorpha 

 group, perhaps into the ^'icinity of the Octodontidae. The Bats rank 

 very low so far as the eye is concerned, possibly on account of their 

 nocturnal habits. Among the Marsupials the Diprotodontia are 

 decidedly lower than the Polyprotodontia chiefly on account of the 

 high degree of development of the eyes of the Didelphidse and 

 Dasyimd^. Since we meet with genera of the lowest type along with 

 others of the highest tjrpe of retinal vascidarisa^on, and again some 

 ^Wthout and others with the additional relic 'of specialisation of a 

 Tapetum, it follows that the details of the vascularisation and of the 

 Tapetum have been developed independently in the various main 

 branches of the Mammalia. 



In fine, the whole Fundus oculi affords a striking illustration of the 

 working of progressive eA'olution, an example all the more valuable, 

 since it illustrates the direct modifying effect of external factors upon 

 a highly specialised organ — in the present case the continued influence 

 of light upon the eye. 



" The Infl-uence of Increased Atmospheric Pressure on the Circula- 

 tion of the Blood. (Preliminary Xote.)" By Leoxaed Hill, 

 M.B. Communicated by Dr. Mott, F.E.S. Eeceived March 

 22,— Eead May 17, 1900. 



Paul Bert"^ recorded the arterial pressm^e in two dogs which he 

 introduced, together with the kymograph, into a chamber, and sub- 

 mitted to a -i- pressure of 53 cm. Hg. The atmospheric pressure was 

 raised to this height in the course of three-quarters of an hour. The 

 mean arterial pressure rose in one dog 16 mm. Hg., in the other 

 46 mm. Hg. ; the pulse frequency fell in the first from 216 to 200, 

 and the respiration from 41 to 29 per minute. The respiratory oscil- 

 lations of blood-pressure became increased, Bert ascribes the results 



* ' Pressiou Barom 'trique,' Paris, 1878, p. 838. 



