Whooping-cough, according to the recent observations of Meunier, also belongs to the small number of diseases which are accompanied by a pronounced lymphæmia. In the convulsive period of this disease both the polynuclear cells and the lymphocytes are increased, the latter in preponderating amount. The former cells are increased to twice, the lymph cells to four times their normal amount. Doubtless in these cases also the lymphocytosis is due to the stimulation and swelling of the tracheobronchial glands.
An increase of the lymphocytes from chemical stimuli is exceedingly rare, though, as is well known, a large number of substances (bacterial products, proteins, nucleins, organic extracts, and so forth) can call forth a polynuclear leucocytosis. In quite isolated cases, an increase of the lymphocytes in the blood in consequence of the injection of tuberculin into tuberculous individuals has been seen. (E. Grawitz.) From the rarity of these cases it can scarcely be doubted that here a tuberculous disease of the glands also plays a part, so that the increased immigration of lymphocytes is brought about not by a chemical property of the tuberculin but by the extensive specific reaction of the diseased glands.
Only one single substance has so far been mentioned in the literature as capable in itself of producing a lymphocytosis. Waldstein asserts that he has produced by injection of pilocarpine, a lymphæmia which undergoes a progressive increase with a rise in number of the injections.
The origin also of lymphocytosis is therefore sharply marked off from that of the ordinary leucocytosis, which consists in an increase of the neutrophil elements. Whilst the latter is admittedly the expression of chemiotactic action, and arises by action at a distance of soluble substances on the bone-marrow, lymphocytosis is due to a local stimulation of certain glandular areas. Thus in the leucocytosis of digestion, of intestinal diseases of children, we refer it to the excitation of the lymphatic apparatus of the intestine, in tuberculin lymphæmia we recognise mainly a reaction of the diseased lymph glands. Hence we conclude that a lymphocytosis appears when a raised lymph circulation occurs in a more or less extended area of lymphatic glands, and when, in consequence of the increased flow, more elements are mechanically washed out of the lymph glands. The pilocarpine lymphocytosis does not contradict this view, for pilocarpine causes extraordinary though transient variations in the distribution of water, whereby the inflow into the blood of fluid containing lymph cells is increased. We therefore regard =lymphocytosis= as the result of a =mechanical= process; whilst =leucocytosis= is the expression of =an active chemiotactic reaction= of the polynuclear elements.