Hrie Respiration of Fishes 



REV. J. G. WOOD 





Queen Lil 



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Owned by Franklin Barrett 



Photo by* Geo. H. Seip 



In the higher beings, the oxygen which 

 is contained in the atmosphere is brought 

 in contact with the blood in a very beau- 

 tiful manner, and in the act of breathing 

 a very difficult problem is solved. 



How is it possible to allow the atmos- 

 phere to come in contact with the blood 

 without permitting it to escape from the 

 vessels through which it flows? 



This difficulty is surmounted in a very 

 simple manner. A portion of the circu- 

 lating apparatus is so contrived that the 

 vessels are diminished to the minutest 

 possible size ; so small, indeed, that there 

 is only just room for the globules of the 



blood to pass singly. The walls of the 

 vessels are extremely thin and delicate, 

 and are made of a substance which 

 allows the passage of air while it retains 

 the blood. In the larger vessels, such a 

 structure would be impossible, on account 

 of the pressure to which the walls are 

 subjected by the volume of blood that 

 rushes through them ; but in those parts 

 which are exposed to the air, the cur- 

 rents are so minute that they exercise 

 comparatively little force, and are easily 

 contained within their delicate walls. 



It is, of course, an important point 

 that a very large surface should be ex- 



