708 DISEASES OF THE SPLEEN. 



depositions. Occasionally these centres undergo change, and 

 small or large abscesses occur. 



Enlargement of the Spleen. — In the horse, in this country, 

 true hypertrophy of the spleen, apart from the existence of un- 

 natural growth or deposition, is a rather rare condition ; as the 

 result of the presence of certain adventitious materials in con- 

 nection with excessive development of pre-existing tissues it is 

 rather common. Particularly well-marked forms of over- 

 growth or enlargement, not of true hypertrophy, are seen in 

 the local manifestations of what are probably general diseased 

 conditions — lymphadenoma and melanosis. The probability 

 that these are only parts of a general diseased condition seems 

 strengthened when we know that similar growths or deposits 

 are found in other organs, as the lungs, the liver, the kidneys, 

 and the lymph-glands. 



Of both these conditions the pathology, as far as their origin 

 is concerned, is doubtful, it being yet undetermined whether 

 we are to regard them as a general vitiation of the system or as 

 proceeding from a local centre to systemic contamination. In 

 many instances they would seem to start in particular organs, 

 and thence spread to others. Their existence is probably 

 more largely encountered in the old than the young. 



Of Lymphadenoma, when producing enlargement of the 

 spleen or any other organ, its physical characters are not those 

 of a uniform infiltration or diffusion through the organ, but 

 rather of a collection of the particular growth in more or less 

 well-defined rounded masses, some of which appear distinctly 

 encapsuled, giving to the external surface a nodulated appear- 

 ance. 



These masses vary in size from a hazel-nut to that of an 

 orange, are of a greyish-white colour and firm consistence, 

 although in this latter character they are variable. Examined 

 more carefully, these products or new material seem to differ 

 from cancer, tubercle, and amyloid infiltration, having physical, 

 histological, and clinical features peculiarly their own. They 

 are probably to be regarded rather as hypertrophy of the par- 

 ticular gland-structure with an increase of lymphoid elements. 



In their origin it is difficult to tell whether the lymph- 

 glands are first diseased, and from them the infective material 

 is conveyed by the lymph-stream to the spleen ; or if the dis- 



