the Fhjsiology of the Egg. 3Q9 



'tlieir eyes." If any further testimony be necessary to show tliat 

 •the augmentation of muscular energy is the result of a nice 

 combination of oxygen with the animal organs, many interesting 

 •facts might be adduced in confirmation of its truth. We gene- 

 rall}'^ find the strength of an animal proportionate to the extent 

 of its chest : hence an attention to the " owz/ho5m/« pectus" has 

 been attended with the improvement of our breed of cattle; and 

 it is in consequence of a great extent of pneumatic receptacle 

 that birds are enabled to bear the prodigious muscular exertion 

 of flight. Is it not probable, too, that the repeated suspirations 

 of the fatigued are instinctive exertions to procure a greater 

 proportion of oxygen, by which their muscular energy may be 

 revived ? I must not quit the subject of this follicle, without no- 

 ticing a very curious fact well known to every one employed in the 

 concerns of a farm-yard, — that, if the obtuse extremity of an egg 

 be perforated with the point of the smallest needle, (a stratagem 

 which malice not unfrequently suggests,) its generating process 

 is arrested, and it perishes like the subventatieoiis egg. Hence 

 Sir Busick Harwood was led to suspect that the elastic fluid 

 contained in the air-bag was oxygen, and I was induced to 

 examine its nature. Can this curious problem 'be solved, by 

 supposing that the constant ingress of fresh air is too highly ex- 

 citing .? A parallel example may be adduced from the vegetable 

 kingdom in support of such an opinion. The young and tender 

 plant, before it puts forth its roots, is often destroyed by having 

 too free a communication with the atmosphere, by which its 

 powers are exhausted : it is to obviate such an effect, that the 

 horticulturist, taught only by experience, covers it with a glass, 

 by which he limits the extent of its atmosphere, and conse- 

 quently decreases its respiration, transpiration, and the inordinate 

 actions which would prove fatal to it. 



vol. X. 2 s I shall 



