BIOLOGICAL EVIDENCE OF MAN'S EVOLUTION Blood Tests.—Not only are the bodies of man and anthropoid apes fashioned on similar lines, but, as was demonstrated at the beginning of the present century, their living tissues give like reactions. In 190o Dr. Hans Friedenthal injected a small amount of human blood into the veins of a chimpanzee ; its vital qual ities were so similar to those of the chimpanzee that no disturb ance followed the operation. When an equal amount of the blood of a macaque monkey was injected into the veins of the chimpanzee there was a slight reaction; the corpuscles of the macaque's blood were destroyed and ejected by the kidneys. When the blood of an ox was used a violent reaction was pro duced, the foreign blood being destroyed and thrown out.
Prof. G. H. F. Nuttall, of Cambridge university, thereafter elaborated a more precise method of estimating blood-affinities, by which very small quantities of blood can be tested against specially prepared antisera. In 1904 appeared his classical work Blood Immunity and Blood Relationship, containing the results of tests carried out on three species of anthropoid apes, 28 species of Old World monkeys, and nine species from the New World. The blood of all these species was tested against a human anti serum. The blood of the anthropoids gave a full reaction-1 00%; that of the Old World monkeys gave a lesser reaction or pre cipitation, one equivalent to 92% of the full; that of the New World monkeys 78%. At the time Prof. Nuttall was making these investigations in England, Dr. Uhlenhuth was carrying out independent enquiries in Germany, and reached corresponding conclusions as to degrees of affinity. The tests devised by Nut tall and by Uhlenhuth utilize the fluid or serum of the blood.
Recently Drs. Landsteiner and Miller (Jour. Experim. Med., vol. xlii., p. 841, 1925) have utilized the corpuscular elements of the blood and find that they give more delicate reactions than those given by the serum. They devised tests which serve to distinguish the blood of the chimpanzee from that of man, but which fail to discriminate the blood of the white man from that of the negro.
Disease Reactions.—The reactions of living tissue are also tested by disease. Man is peculiarly susceptible to syphilis; the animals most akin to him in this respect are the great anthropoid apes. Monkeys are difficult to inoculate with syphilis, and when they suffer, take the disease in its mildest Anthropoid apes are almost as susceptible to typhoid fever as man is. When chim panzees are kept in confinement they are liable to that modern disease of man—appendicitis. Anthropoids react to stimulants, sedatives and poisons in the same manner as human beings. The brains of the great anthropoid apes are smaller and are less con voluted than is the case in man, yet when the living cortex is stim ulated by electrical methods, be it in man or anthropoid ape, the same reactions follow when corresponding convolutions are ex cited. Surgeons have found that observations made by experi mental physiologists on the brains of anthropoid apes afford reliable guidance when they have to operate on the brain of man.