or Bed Disks of the Mammiferous Animals. 27 



puscles from the right ventricle, dried, all about l-4000th 

 of an inch in diameter. 



11. Water Rat, adult, [Miis amphihius). Blood from both 

 ventricles, examined dry ; average-sized corpuscles l-^OOOth 

 and l-3600th of an inch diameter. 



12. Common brown House Rat, a male, nearly full-grown, 

 [Mils decumanus). Common size of corpuscles from right ven- 

 tricle l-4000th to l-355tth of an inch. 



13. Common Mouse, [Mus musctdus). l-4000th and 

 l-3600th common sizes. Extreme diameters l-5333rd and 

 l-3000th. Blood from heart and vena cava. 



a. Foetus, about half an inch long, from the uterus of the 

 above mouse. 1 -2666th the most frequent size, and many 

 smaller corpuscles from l-5333rd to l-4000th, the latter being 

 numerous. Many of the corpuscles more globular than usual, 

 that is, more like spheres than disks, — a common appearance 

 in the foetal blood of mammals at an early period. 



From this and several other observations, the comparatively 

 large size of the blood corpuscles in the foetus becomes mani- 

 fest. The fact is important, because it is connected with the 

 comparative condition of the respiratory organs, and, more- 

 over, illustrates the difference between the blood of the parent 

 animal and that of the foetus ; so that if there be any commu- 

 nication between the vessels of the placenta and uterus, the 

 blood of the mother and foetus is at all events different. 1 have 

 examined the foetal blood of the human subject, obtained from 

 the heart, placenta, and umbilical vessels, with the same result 

 as above ; and it appears to me to be of considerable interest*. 



14<. Common Guinea Pig, adult male, [Cavia Cohaya), 

 Corpuscles from the right ventricle, generally measuring 

 from l-4000th to l-3200th of an inch. 



15. Dom.estic Rabbit, adult female, [Lepus cimiculus). 

 Most common diameter l-iOOOth; extreme sizes l-5000th 

 and l-3200th of an inch. 



16. Golden Agouti, adult male, [Dasyprocta aurata). 

 l-3600th the most common diameter. Extreme sizes l-5333rd 

 and l-3200th. Blood from a vein of the ear. 



17. Acouchi, full-grown, [Dasyprocta acoiichi). 1 -3600th 

 a common diameter, as was also l-4000th. Extreme sizes 

 l-4572nd and ] -3200th. 



18. White-whiskered Paradoxure, adult, (P. Leucojnystax). 

 Size of corpuscles very variable; most commonly l-4365th 

 and l-4000th. Extreme diameters l-6000th to l-3200th. 

 Blood from a prick of the tail. 



* The accurate Hewson' observed the same fact in a fowl and in a 

 viper. (Exp. Inquiries, part iii. p. 39.) 



