The liver in relation to protozoal infections

Abstract

I thought that before writing this paper I should consult some standard works on the liver and its diseases ; what was my surprise when I found that not a single word in these books referred to protozoal diseases, in spite of t h e fact that malaria, for instance, is the greatest single cause of morbidity in the human race ; so perhaps this approach to the subject is not inopportune. I do not intend to discuss, this evening, all the Protozoa Which affect the liver ; in, fact, I am excluding nearly all the organisms which cause extensive damage to its substance, such as Entamoeba histolytica which gives rise to amoebic abscesses, or Histomonas meleagridis producing blackhead in turkeys or Leishmania donovani, the cause of kala-azar. The group of Protozoa that I am going to refer to are the Sporozoa, the class which includes the malaria parasites. Recent work on the life history of these organisms---chiefly by the President of our Society--has brought the liver very much into the limelight. First I must say a little about the organ itself. The liver is the largest gland in the body and is indispensable to life. It is composed of lobules about 2 mm. in diameter, each lobule consisting of columns of parenchyma cells. Around each lobule is connective tissue wherein travel branches of the portal vein, hepatic ar tery and bile duct. In the centre of each lobule is a branch of the hepatic vein. The two circulations meet in the sinusoids between the columns of liver cells. The sinusoids are lined by the strongly phagocytic Kupffer cells and ordinary endothelium ; it is improbable that the blood comes into direct contact with the parenchyma itself. The liver develops as a ventral outgrowth of the endoderm of the duodenal portion of the mid-gut. It projects itself into a mass of undifferentiated mesoderm via which it becomes vascularized and from which it obtains its connective tissue framework. These two elements--the mid-gut endoderm and