568 Veterinary Medicine. 



cally in connection with active digestion in the first four or five 

 hours after an abundant meal, and especially at intervals of a 

 minute, during what may be called the diastole of the viscus. 

 The supply of blood is also much greater in the well fed animal, 

 than in the emaciated and impoverished one. 



Pathological hyperemias of a passive kind may occur as the re- 

 sult of obstructions in the veins leading from the spleen, such as 

 the splenic veins, the posterior vena cava, or that part of the 

 portal vein comprised between its junction with the splenic and 

 the liver. Diseases of the right heart or its valves, of the lungs 

 (emphysema), or of the liver which hinder the onward flow of 

 blood and increase the blood tension in the vena cava or portal 

 vein have a similar action. Perhaps we should include inhibition 

 of the nerves (splanchnic, vagi) and nerve centres (medulla ob- 

 longata, cerebral cortex) which preside over the contraction of 

 the splenic vascular walls, and of the capsular and trabecular 

 muscles. There is reason to believe that the ptomaines and 

 toxins of several microbian diseases, operate through these 

 centres, while other such microbes and toxins operate directly on 

 the spleen itself. 



Active congestions of the spleen are most commonly associated 

 with microbian diseases and may be attributed partly as above 

 stated to the action of the toxic products on the contraction nerve 

 centres, and on the splenic vessels and parenchyma, but also in 

 no small degree on the active proliferation of the germs them- 

 selves in the splenic pulp, and of the splenic cells. Among the 

 most notable instances of this kind are, in man, malarious, yel- 

 low and typhoid fevers, and, in animals, anthrax, and Southern 

 cattle fever. In most febrile diseases, however, there is a ten- 

 dency in this direction, which may be fairly attributed to the 

 paresis of the organ and the delay of the blood in its pulp chan- 

 nels and spaces with the consequent local increase of microbes 

 and toxins, The microorganisms can usually be found abun- 

 dantly in such cases, in the liquid of the pulp, and in the inte- 

 rior of the leucocytes and other cells that go to make up its solid 

 constituents. 



It has been long recognized by veterinarians that acute con- 

 gestion often arises in connection with a sudden transition from a 

 poor or insufficient diet to an abundant and nutritious one and 



