| | | ternal organs only -------------+------------------+------------------+------------------- Alterations |Almost normal |Pale and |Corpuscle may be in | | hypertrophied. | shrunken and dark, erythrocytes| |Schüffner’s dots | or may be colour- | | seen in deeply | less. Maurer’s | | stained specimens| coarse dots some- | | | times seen -------------+------------------+------------------+------------------- Essentially the method of cultivation, as used by Thomson, is as follows: 10 c.c. of infected blood are drawn from a vein and transferred to a sterile test tube, in which is a thick wire leading to the bottom of the tube. One-tenth of a cubic centimetre of a 50 per cent. aqueous solution of glucose or dextrose is placed in the test tube, preferably before adding the blood. The blood is defibrinated by stirring gently with the wire. When defibrination is complete the wire and the clot are removed, and the glucose-blood is transferred, in portions, to several smaller sterile tubes, each containing a column of blood about one inch in height. The tubes are plugged and capped and then transferred, standing upright, to an incubator kept at a temperature of 37° C. to 41° C. The blood corpuscles soon settle, leaving a column of serum at the top, to the extent of about half an inch in each tube. The leucocytes need not be removed by centrifugalization. J. G. Thomson (1913) and his collaborators did not find it necessary to destroy the complement in the serum, and they found that the malarial parasites developed at all levels in the column of corpuscles, and not merely on the surface layer of the corpuscles as first stated by Bass and Johns. So far only the asexual generation of the malarial parasites has been grown _in vitro_. Thomson rarely observed hæmolysis in the cultures. Clumping of the malignant tertian parasites occurred. In cultures of the benign tertian parasite (_Plasmodium vivax_) clumping was not observed. J. G. and D. Thomson consider that this difference as regards clumping explains why only young forms of malignant tertian are found in peripheral blood, as the clumping tendency of the larger forms causes them to be arrested in the finer capillaries of the internal organs. It also explains the tendency to pernicious symptoms, such as coma, in malignant tertian malaria. Further it was found from cultures that _P. falciparum_ was capable of producing thirty-two spores (merozoites) in maximum segmentation, while _P. vivax_ produced sixteen spores (merozoites) as a rule, though the number might be greater than sixteen. (Quartan parasites produce eight spores or merozoites in schizogony.)