174 ON GENERATION. 



the office of the diaphragm, which, indeed, of itself, and without 

 the assistance of the abdominal muscles, were incompetent to 

 act as an instrument of respiration. And, then, the diaphragm 

 has another duty to perform in those creatures in whom it is 

 muscular or fleshy, viz., to depress the stomach filled with food, 

 and the intestines distended with flatus, so that the heart and 

 lungs shall not be invaded, and life itself oppressed in its cita- 

 del. But as there was no danger of anything of this kind in 

 birds, they have a membranous septum, perfectly well adapted 

 to the purposes of respiration, so that they have very properly 

 been said to have a diaphragm. And were birds even entirely 

 without anything in the shape of a diaphragm, still would 

 Aristotle not be liable to criticism for speaking of the ova 

 commencing at the septum transversum, because by this title 

 he merely indicates the place where the diaphragm is usually 

 met with in other animals. In the same way we ourselves 

 say that the ovary is situated at the origin of the spermatic 

 vasa prseparantia, although the hen has, in fact, no such 



The perforations of the lungs discovered by me (and to which 

 I merely direct attention in this place,) are neither obscure nor 

 doubtful, but, in birds especially, sufficiently conspicuous, so that 

 in the ostrich I found many conduits which readily admitted 

 the points of my fingers. In the turkey, fowl, and, indeed, 

 almost all birds, you will find that a probe passed downwards 

 by the trachea makes its way out of the lungs, and is disco- 

 vered lying naked and exposed in one or another of the abdo- 

 minal cells. Air blown into the lungs of these creatures with 

 a pair of bellows passes on with a certain force even into the 

 most inferior of these cells. 



We may even be permitted to ask, whether in man, whilst he 

 lives, there is not a passage from openings of the same kind into 

 the cavity of the thorax ? For how else should the pus poured 

 out in empyema and the blood extravasated in pleurisy make 

 its escape ? In penetrating wounds of the chest, the lungs 

 themselves being uninjured, air often escapes by the wound ; 

 or liquids thrown into the cavity of the thorax, are discharged 

 with the expectoration. But our views of this subject will be 

 found fully expressed elsewhere, viz., in our disquisitions on the 

 Causes, Uses, and Organs of Respiration. 



