5o6 



NATURE 



[March 31, 1892 



cellular animals to the Metazoa, and his embryological 

 theory of the " phagocytella." The reaction of the 

 mesodermic phagocytes of sponges to foreign matters 

 introduced into the substance of these animals is de- 

 scribed ; and, subsequently, similar phenomena in Ccelen- 

 tera, Echinoderma, and Worms are cited, and illustrated 

 by original drawings. It is shown that in these Inverte- 

 brates the phagocytes attack and invest, either singly or 

 in fused masses, not only inorganic particles, but large 

 parasites, and also intrusive parasitic Bacteria. Thence 

 he passes to organisms — the MoUusca, Arthropoda, and 

 Tunicata — which have a well-developed blood-system- 

 He shows that here, too, there are no special " vascular " 

 phenomena excited by conditions which in higher Verte- 

 brates produce " inflammation," but solely a " phagocyte 

 reaction " or resistance. Numerous cases of infectious 

 bacterial and fungal diseases in Arthropoda are described, 

 and the action of the phagocytes in combating the in- 

 trusive parasites by ingulfing and digesting them is 

 demonstrated. Even when we come to the Vertebrates, 

 it is shown that, in regions of the median fin of the tad- 

 pole of the Axolotl, an inflammation can be excited 

 which is purely phagocytic, and in which the blood- 

 vessels and their contents take no part. 



The peculiarity, however, of inflammatory processes in 

 adult and higher Vertebrata is, that the blood-vessels 

 come into play. The amoeboid corpuscles floating in the 

 blood by active movement (of a chemiotactic nature), 

 push their way through the walls of the capillaries (diape- 

 desis) in the region which is infected or injured, and join 

 their forces to those of the tissue phagocytes in investing 

 and destroying the injurious particles. 



A detailed study of the leucocytes of the blood and 

 lymph of Vertebrates follows, which are distinguished as 

 (i) lymphocytes, (2) uninuclear, (3) eosinophil, and (4) 

 neutrophil or multinuclear leucocytes. Metschnikofif 

 shows that the two varieties of leucocytes which play the 

 chief part in inflammation — viz. the uninuclear and the 

 neutrophil — are endowed with a marked chemiotactic and 

 physiotactic sensibility, are capable of amoeboid move- 

 ments, and apt to ingulf and to digest various foreign 

 bodies, notably many kinds of living Bacteria. In the 

 Amphibia he shows that the multinuclear leucocytes can 

 transform themselves into the uninuclear form, and be- 

 come fixed cells of the connective tissue. In Vertebrates 

 generally, uninuclear leucocytes can be transformed into | 

 epitheUoid and giant cells. What is true of leucocytes ■ 

 is also true of other migratory cells. 



The ninth, tenth, and eleventh lectures deal with such 

 topics as the endothelium of vessels, the dilatation of 

 vessels, chronic inflammations — tubercle being taken as a 

 type — serous inflammation, bactericidal power of serous \ 

 humours and exudations ; and the antitoxic property of 1 

 the serum. ^ A most important and interesting study of j 



' I cannot let pass this opportunity of pointing out an evolutional parallel 

 in the history of phagocytes which tends to harmonize to some extent the 

 views of those who insist on the bactericidal and the anti-toxic properties of 

 serum, wiih MetschnikofTs view that the phagocytes are of prime import- 

 ance. In the recent debate at the Pathological Society of London, it was 

 pointed out by several speakers that even if it be ad nitted that the serum 

 and exudations have, in relation to certain special cases, these properties — 

 or rather contain substances having these properties — those substances must 

 be derived from the living cells of the organism, and probably from leuco- 

 cytes. The parallel to which I refer is that of intra-cellular and cavitary 

 digestion. The alimentary canal of some lower animals is lined by phago- 



the phenomena of resistance to the tubercle bacillus on 

 the part of the giant-cells of the Algerian Rodent Meri- 

 ones Shaivi is given in some detail. 



The last lecture treats of some previous theories of 

 inflammation, summarizes the facts which serve to estab- 

 lish what Metschnikofif calls the biological theory of 

 inflammation, and repels some attacks recently made on 

 it. The theory is formulated in these words : " Inflam- 

 mation must be looked upon in its entirety as a phago- 

 cytic reaction of the organism against irritative agents— 

 a reaction which sometimes is carried out by wandering 

 phagocytes only, sometimes with the assistance of the 

 vascular phagocytes or with that of the nervous system." 

 The last words refer to the intervention of the vaso-motor 

 nervous centres. 



Medicine, says our author in order to gain her 

 assigned objects must make use of knowledge drawn 

 from all less complicated branches of science ; and 

 amongst others from that biology which studies organisms 

 in their living state and their natural evolution. 



The services rendered will be reciprocal. General 

 biology, he points out, can gain great advantage by 

 embracing in the sphere of its studies the morbid pheno- 

 mena now relegated to the pathologist. Too often biology 

 finds difficulties in the study of the processes of evolution 

 because the phenomena are presented to the observer in 

 an already accomplished form. To observe with clear- 

 ness the play of the general law of natural selection, we 

 must study the less stable phenomena, the less perfected 

 organizations — in a word, the phenomena in which natural 

 selection can be observed every day. Now it is precisely 

 the phenomena of disease and the reactions connected 

 with it— the struggle between the organism and its 

 aggressors— which offer the best opportunity for a close 

 study of the operation of natural selection. 



It has been impossible to do justice to this remarkable 

 book in a short review. It has the special quality of 

 carrying conviction to the reader's mind by the fact 

 that every assertion is supported by a number of well- 

 chosen observations or experiments which are described 

 with a lucidity and precision characteristic of a man 

 thoroughly familiar with the minutest details of the things 

 of which he speaks. It is to be hoped that it may have, 

 amongst other consequences, that of silencing certain 

 medical "educationists," who deny that zoology is a 

 necessary or useful accompaniment of the chemical and 

 physical study of living things. Its pages contain con- 

 vincing proof that medicine has gained more real know- 

 ledge and practical help from modern zoology than 

 from the elaborate experimentation on higher Vertebrates 

 which is directed by narrow-minded ignorance of the 

 simpler expressions of animal organization. 



E. Ray Lankester. 



cytes, which individually ingulf solid pa 

 means of ferments, acids, &c., formed within the phagocytes. A later stage 

 of evolution of the digestive system consists in the discharge by these cells 

 of the food-dissolving substances elaborated by them into the common liquid 

 occupying the cavity which they surround. The food dissolving substances 

 are no longer found exclusively in the cells, but in the liquid which bathes 

 them. Yet no one ascribes a .s/^c/a/ power to the gastric juice, or hesitates 

 to trace its qualities to the transformed intra-celluiarly-digesting cells, bo 

 with bactericidal and anti-toxic juices: they must be traced (when their 

 existence is proved) to the modification of' the modiis operandi of intra- 

 cellularly-digesting phagocytes. 



NO. I I 70, VOL. 45] 



