The Menstruation and Ovulation of Macacus rhesus. 203 



blood is found in the uterine cavity ; the menstrual clot is formed 

 during Stage VII, and the torn mucosa is healed in the final, Stage 

 VITI. 



Histology. The uterus consists of an internal mucosa and external 

 muscular layers ; the mucosa is composed of uterine and glandular 

 epithelium, blood vessels, and stroma. The uterine epithelium lines 

 the surface of the stroma, the glandular epithelium lines pits in the 

 stroma and is continued into branches of those pits which extend 

 from their lower end into the deeper part of the stroma. 



The stroma itself is a delicate connective-tissue-like layer ; the 

 internuclear protoplasm is drawn out into delicate processes which 

 form a continuous network, and there is no intercellular substance. 



The histological changes which take place during the menstruation 

 of Macacus rhesus are very similar to those which I have already 

 described in a former paper, *' The Menstruation of S&mnopithecus 

 entellus ('Boy. Soc. Proc.,' vol. 54, and 'Philosophical Transactions,' 

 vol. 185). Work similar to that which I have already described for 

 S. entellus has been undertaken for Macacus rhesus, and the phenomena 

 compared step by step. While it has been thought advisable to note 

 the points of similarity and of difference which occur in the menstrua- 

 tion of these two species, and to point out the fact that the results 

 arrived at by the study of the menstruation of Macacus rhesus entirely 

 confirm the results which my examination of 8. entellus led me to 

 publish, I have purposely avoided all unnecessary repetition and have 

 been obliged in consequence to assume some knowledge of the details 

 given in my former papers. It is all the more important to publish 

 this account, as the results which I have arrived at differ in some 

 important particulars from the accounts of menstruation which have 

 been generally accepted. 



Stage I. The mucosa of Macacus rhesus is thicker and the proto- 

 plasmic network denser, the glands more numerous and more 

 branched than is the case in 8. entellus. I find no radial fibres. 



Stage II. There is a great increase in the number of nuclei by 

 amitotic division and fragmentation. Hyperplasia occurs. The 

 mucosa becomes much swollen. 



Stage III. The vessels increase in number and size, and they are 

 congested. There is an increase of leucocytes. 



Stage IV. Hypertrophy of the walls of the vessels in the super- 

 ficial part of the mucosa, followed by degeneration, occurs ; 

 the small vessels break down and extravasation of blood takes 

 place. There is no sign of the migration of leucocytes. 



Stage V. Lacunaa are formed at first some distance below the 

 epithelium, but they gradually displace the intervening tissue 

 and come to lie directly below the uterine epithelium. 



VOL. LX. Q 



