FUNCTIONS OF THE SPLEEN. 477 



State of our Knowledge concerning the Functions of the Spleen. -The spleen is al- 

 most universal in vertebrate animals ; it is an organ of considerable size, and is very 

 abundantly supplied with vessels and nerves ; it has a complex structure, unlike that of 

 any of the true glands ; its tissue presents a variety of proximate principles ; but it has 

 no excretory duct, and no opportunity is afforded for the study of its secretion, except 

 as it may be taken up by the current of blood. It must be admitted, also, that, up to 

 the present time, no definite physiological ideas have followed the elaborate microscopi- 

 cal and chemical examinations of the spleen. There have been only two methods of 

 inquiry, indeed, which have promised any such results : First, a comparison of the blood 

 and lymph going into and coming from the spleen, and an examination of the variations 

 in the volume of the organ during life ; and second, a study of the phenomena which fol- 

 low its extirpation in living animals. A review of the literature of the subject will show 

 that we have gained but little positive information from either of these methods of study. 



The condition of the question of the influence of the spleen upon the composition of 

 the blood is well illustrated in the last edition of Longet's elaborate work upon physiology. 

 This author quotes opinions of the highest authorities, based chiefly upon microscopical/ 

 investigations, some in favor of the view that the blood-corpuscles are destroyed, and 

 others arguing that they are formed in the spleen, while he himself offers no opinion 

 upon the subject. Still, there are certain established points of difference between the 

 blood of the splenic artery and of the splenic vein. There can be little doubt of the fact 

 that the blood coming from the spleen contains a large excess of white corpuscles ; but 

 it can by no means be considered as settled that the function of the spleen is to form 

 white blood-corpuscles. In pathology, although great increase in the leucocytes of the 

 blood frequently attends hypertrophy of the spleen, this condition is also observed when 

 the spleen is perfectly healthy. 



Diminution in the proportion of red corpuscles in the blood in passing through the 

 spleen, in a very marked degree, has been noted, and this gives color to the supposition 

 that the spleen is an organ for the destruction of the blood-corpuscles ; but we know 

 nothing of the importance or significance of this process, and it is not shown that the 

 corpuscles exist in undue quantity in animals after the spleen has been removed. We 

 learn nothing more definite from the fact that the blood of the splenic vein seems to contain 

 an unusual quantity of pigmentary matter. In connection with the marked diminution 

 in the proportion of blood-corpuscles, physiologists have observed a marked increase in 

 albuminoid matters in the blood of the splenic vein. 



The significance of the facts just stated is so little understood, that it would seem 

 hardly necessary even to mention them, except as an illustration of the small amount of 

 definite information regarding the functions of the spleen that has resulted from an 

 examination of the blood coming from this organ. We know nothing of any changes 

 effected by the spleen in the constitution of the lymph. 



Variations in the Volume of the Spleen. One of the theories with regard to the 

 function of the spleen, which merits a certain amount of consideration, is that it serves 

 as a diverticulum for the blood, when there is a tendency to congestion of the other 

 abdominal viscera. 



It has been shown that the spleen is greatly enlarged in dogs, from four to five hours 

 after feeding, that its enlargement is at its maximum at about the fifth hour, and that it 

 gradually diminishes to its original size during the succeeding twelve hours ; but it is not 

 apparent how far these changes are important or essential to the proper performance of the 

 functions of digestion and absorption. Experiments have shown that animals may live, 

 digest, and absorb alimentary principles perfectly well after the spleen has been re- 

 moved, and this has even been observed in the human subject ; and, in view of these facts, 

 it is impossible to assume that the presence of the spleen, as a diverticulum for the blood, 

 is essential to the proper action of the other abdominal organs. 



