BLOOD-COEPUSCLES 1037 



Thus, in their early state, in which they seem to be identical with 

 the corpuscles found floating in chyle and lymph, they seem to be 

 nearly homogeneous particles of protoplasmic substance, but in 

 their more advanced condition, according to Dr. Klein, their sub- 

 stance consists of a reticulation of very fine contractile proto- 

 plasmic fibres, termed the ' intracellular network,' in the meshes of 

 which a hyaline interstitial material is included, and which is con- 

 tinuous with a similar network that can be discerned in the substance 

 of the single or double nucleus when this comes into view after the 

 withdrawal of these corpuscles from the body. In their living state, 

 however, whilst circulating in the vessels, the white corpuscles, 

 although clearly distinguishable in the slow-moving stratum in 

 contact with their walls (the red corpuscles rushing rapidly 

 through the centre of the tube), do not usually show a distinct 

 nucleus. This may be readily brought into view by treating 

 the corpuscles with water, which causes them to swell up, 

 become granular, and at last 

 disintegrate, with emission of 

 granules which may have been 

 previously seen in active mole- 

 cular movement within the 

 corpuscle. When the white 

 corpuscles in a drop of freshly 

 drawn blood are carefully 

 watched for a short time, they 

 may be observed to undergo 

 changes of form, and even 

 to move from place to place, 

 after the manner of Amcebcu. 



When thus moving they p IG . 7 69.-Altered white corpuscle of blood 

 engulf particles which lie an hour after having been drawn from the 

 in their course such as finger, 

 granules of vermilion that 



have been injected into the blood-vessels of the living animal and 

 afterwards eject these in the like fashion. 1 Such movements will 

 continue for some time in the colourless corpuscles of cold-blooded 

 animals, but still longer if they are kept in a temperature of about 

 75. The movement will speedily come to an end. however, 

 in the white corpuscles of man or other warm-blooded animals. 



1 Metschnikoff has made the highly interesting and important observation that the 

 immunity of certain animals to certain diseases appears to be due to the power that the 

 white corpuscles possess of acting as 'phagocytes,' or eating the germs of the disease. 

 Metschnikoff found that the virulent rods of the Bacillus of anthrax ' when intro- 

 duced by inoculation into an animal liable to take the fever, such as a rodent, were 

 absorbed by the blood-cells only in exceptional instances. They were readily absorbed 

 by the blood-cells of animals not liable to the disease, as frogs and lizards, when the 

 temperature was not artificially raised (fig. 770), and then disappeared inside the 

 cells. . . . From all these data we must assume with Metschnikoff that the Bacillus 

 is harmless because it is absorbed and destroyed by the blood-cells, and injurious 

 because this does not happen; or at least that it becomes harmless if the destruction 

 by the blood-cells takes place more rapidly, and to a greater extent than the growth 

 and multiplication of the Bacillus, the converse being also true ' (see A. de Bary, 

 On 1-li/rti'i-iii, English edition, p. 130). The importance of phagocytes is becoming 

 more and more recognised by the pathologist. 



