V. DIMINUTION OF THE WHITE BLOOD CORPUSCLES (LEUKOPENIA).
Diminution of the white blood corpuscles plays--comparatively with their increase--a very unimportant _rôle_ in clinical observations. It occurs in but few groups of diseases, and but seldom attains a marked degree. Koblanck has described a most marked fall in the number of the colourless cells, in the following remarkable blood condition. In a strong man, 25 years of age, whose internal organs were found to be healthy, short epileptiform attacks occurred, in one of which death took place. The autopsy gave no indication of the cause of death. Two examinations of the blood were made in the course of the three days he was under observation. In one of these, out of =ten cover-glass preparations, not a single white blood corpuscle was found=, and in the second only one example.
We have mentioned this case here, because it is remarkable as an extreme leukopenia never before observed. An explanation however is impossible owing to the obscurity of the general clinical condition.
For the rest the conditions, under which a considerable diminution of the leucocytes occurs, are very well-known. We distinguish two chief groups:
1. Leukopenia from =destruction of a portion of the white blood corpuscles= (Löwit);
2. Leukopenia from =deficient inflow of white corpuscles=:
[alpha]. in infectious diseases from =negative chemiotaxis=;
[beta]. in anæmia etc. from =defective action of the bone-marrow=.
We have entered more fully into the leukopenia experimentally produced by Löwit, in the chapter on leucocytosis. We there explained, that according to present views, we have to deal, not with an actual destruction of the white elements, but merely with an altered distribution within the blood-stream.
Amongst the infectious diseases where an hypoleucocytosis occurs, typhoid fever must first be mentioned. The diminution is chiefly at the expense of the polynuclear cells. Uncomplicated measles too, generally runs its course with a marked leukopenia, specially distinct during the breaking out and at the height of the exanthem. These cases of infectious leukopenia are to be explained, not by a destruction of white corpuscles, but rather by a diminished inflow, brought about by the circulation of substances negatively chemiotactic for the polynuclear elements.