EXTRACTS FROM “ THE THEORY OF MENSTRUATION.” 23 
freely imbues the mucous membrane of the vagina. An examina- 
tion of this discharge under the microscope indicates the presence 
of many thin transparent masses, of a honeycomb appearance, 
such as usually characterise the epithelium of mucous surfaces ; 
also may be seen a few corpuscular bodies, having, on comparing 
them with those existing in the circulation of the rabbit, the mi- 
croscopic characters of the blood-discs of that animal. These last, 
however, are very few in number. The fluid, besides the epithe- 
lium, contains in it principally globular bodies, of an ovoid form, 
transparent, and averaging the l-600dth of an inch in diameter. 
The regularity of the return of these symptoms is greatest during 
the spring and summer : as the cold weather approaches it be- 
comes less so. The heat is not noticed during lactation, but re- 
turns as soon as this duty is over : the very next day, perhaps, the 
animal indicates her desire for re-impregnation. 
The oestrum affects the horse, during the early part of summer, 
every fortnight; the desire gradually passes off as autumn ap- 
proaches. I find it existing in the end of July, but it is rare. 
The heat lasts for two or three days, passes away, and returns in 
the period stated. The discharge is often profuse ; it consists of 
a yellow, strong, odorous fluid, of the consistence of oil. Globules, 
various in size, some half a thousandth of an inch in diameter, 
abound in it : all have an ovoid form ; but no nucleus is apparent. 
“ On standing, it separates into a transparent, yellow, serous- 
looking fluid, and a whitish flocculent precipitate. The fluid has a 
mild alkaline re-action, contains alittle albumen, and is rendered tur- 
bid, but does not coagulate by heat and nitric acid. It contains chlo- 
ride of sodium and earthy phosphates. There is no fibrine present.” 
I am indebted for the above analysis, as well as for that which 
follows, to the kindness of my friend, Dr. Day, whose contributions 
on the normal and diseased condition of the urine are well known 
and appreciated. 
I have preserved the fluid for five months in a phial, corked, 
and as yet it shews no signs of putridity. 
I observed a few blood corpuscles in the fluid escaping from a 
mare the day after she had received the male, but in all the ex- 
amples I had for observation I did not detect any previous to co- 
pulation. In this case the sanguineous discharge may have been 
the result of introition : it was a maiden mare. 
I have found that during lactation in the horse, as in the ox and the 
cat,' and, as is well known, in our own species, the development of 
ova occurs, and impregnation takes place. I am acquainted with 
a late example in the horse, where, six weeks after parturition, 
and during lactation, impregnation took place. 
The ox comes into season every three weeks. In old animals 
