EXTRACTS FROM “THE THEORY OF MENSTRUATION.” 25 
fluid with it; it yielded water, 26.9; fibrine, 4.3; fixed salts 0.9 ; 
albumen and other matter destructible at a red heat, 3.9. The 
fibrine was digested in water for a considerable time, and then in 
boiling alcohol and ether : it was afterwards dried till it ceased to 
lose weight. The quantity is remarkable.” 
I have stated that the catamenial fluid in the ox is not always 
sanguineous. It is often transparent, remarkably viscid, and has 
the appearance and consistence of jelly. In new-born calves, the 
cornua and uterus are filled with this transparent secretion. It is 
endowed with great plasticity, and I apprehend it is from this 
quality (when the periodic discharge of oxen, in addition to this 
glairy character, has that of sanguinity superadded) that the blood 
corpuscles readily and universally assume the linear and moni- 
liform arrangement. 
In the dog, the periodic discharge occurs generally every twelve 
or sixteen weeks, and remains for several days; eight or ten com- 
monly. The dog is generally in heat three times a-year, and the 
catamenia follow at intervals, less distant in summer than in 
winter. In many individuals, two periods annually only are ex- 
perienced ; in a few, only one period. I have also found other 
individuals having the secretion appearing every eight or nine 
weeks. 
The sanguineous nature of the discharge in the dog is strongly 
characterised. I have submitted the secretion to a microscopic 
comparison with normal blood, taken from a puncture in the ear of 
an animal whilst menstruating. 
The colourless as well as the red corpuscles were as evident 
in the menstrual fluid as in the blood : of course, the admixture 
of mucus made them appear, in the field of sight, fewer in num- 
ber than in the latter fluid, while the existence of masses of 
epithelium floating with them in the fluid characterised the se- 
cretion. 
That the human female is no exception to the general law, and 
that animals, during menstruation, are fittest for impregnation, was 
a fact known to Aristotle. He expresses clearly his opinion that 
some women are capable at this time only , and not at any other, 
of conception, on account, as he is of opinion, of the womb imme- 
diately closing after the cessation of the catamenia. 
Probably the idea of the closing of the human uterus was sug- 
gested by what really does occur in some of the lower animals. 
In the sheep the os uteri is gristly and cartilaginous ; and when 
the animal is not in heat is hermetically sealed by the close ap- 
proximation of its edges, in the manner of a volute, or rather like 
two of the letters c. In such a condition it is impossible to pass 
VOL. XVIII. E 
