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OBSERVATIONS UPON THE SPLEEN. 



were not enlarged, notwithstanding the large amount of nutritive substances which 

 were received into their circulatory apparatus. 



That the spleen is an organ of subordinate importance in the animal economy 

 will be shown by the following facts : — 



It is absent from all invertebrate animals without exception. It is also absent 

 from the Ampldoxus, the connecting link between fishes and the higher forms of 

 the mollusca. 



In the Ainxjiliioxus and Invertebrate animals the blood-corpuscles are always 

 colorless. The occurrence of the spleen is accompanied by a change in the color 

 of the blood. 



Has the spleen anything to do with the production of the red blood-corpuscles of 

 vertebrate animals? The blood of the invertebrata, with its corpuscles, exists 

 before the formation of any special organs. The same fact is noticed in the 

 development of the foetus of warm-blooded animals. 



A vascular system circulating a fluid containing colored blood-corpuscles exists 

 before the formation of any special organs, and hence it is probable that the spleen 

 has little to do with the formation of the corpuscles and the production of their red 

 color. This conclusion is farther sustained by the fact that the amputation of the 

 spleen of Dogs and other animals is not followed by any alteration in the amount 

 or character of the blood and its constituents, and they enjoy very good health, and 

 there is no sensible diiference between them and those that have not undergone 

 the operation. From these investigations we may draw the following conclusions : — 



1. The spleen of Birds and many Reptiles is too small to exert an important 

 influence in the animal economy. 



2. Its size corresponds in no manner with the number of blood-corpuscles, or the 

 rapidity of the composition and decomposition of the organic and inorganic elements 

 of the fluids and solids of animals. 



3. Of the real office of the spleen in the animal economy we are still ignorant. 



4. The function of the spleen is not indispensable to the maintenance of life. 



