On the Respiration of the Foetus^ etc. 221 



into the mass of the blood, and it does not matter 

 how this is done. And indeed the tepor produced in 

 the egg by the warmth of the incubating fowl 

 produces the same effect in its primogenial juices as 

 the nitro-aerial particles do in the mass of the blood. 

 For just as the nitro-aerial particles passing into the 

 earth along with heat and moisture, effervesce with 

 its saline-sulphureous particles, on which action the 

 life and respiration of plants depend, as has been 

 elsewhere shown, and as nitro-aerial particles densely 

 mixed with the blood through the agency of the 

 lungs excite the fermentation required for animal life, 

 so also the same nitro-aerial particles entering the 

 juices of the Qgg under the form of a genial heat 

 appear to contribute to some extent to set up in them, 

 vital fermentation and animal movement, and so in a 

 measure to perform the part of respiration. And 

 hence it is that the tepor, whether produced by 

 incubation or in some other way, is so necessary for 

 sustaining the life of the chick in the egg. For if an 

 egg is opened after some days of incubation, in such 

 a way that the salient point comes into view, you will 

 find that according as the egg is exposed to heat or to 

 cold, the little heart of the chick is beating in the 

 one case, and in the other languishing and ceasing to 

 move as if respiration were suppressed. 



From what has been said it is not very difficult to 

 understand how it is that the foetus, if wrapped in its 

 unbroken membranes, can live for several hours after 

 birth without danger of suffocation ; while yet if it has 

 once taken air into the lungs after being stripped of 

 its membranes, it will not be able to survive for a 

 single moment without air, but will immediately die, 

 as has been recorded by the illustrious Harvey. It is 

 not enough to say here that the blood of the infant, 



