530 



NA TURE 



[September 28, 1905 



that in recent years it has been assumed by some 

 epidemiologists that the essential factor in the appear- 

 ance and spread of plague is the rat, whereas there 

 exists good evidence that plague was introduced into, 

 and broke out in, a locality in which neither ante- 

 cedently nor concurrently any such epizootic was 

 noticed — to mention, amongst others, the outbreak 

 of plague in Oporto, and in Glasgow, 1900. No one 

 questions the fact that plague has occurred on board 

 ships in which plague rats had been found, nor that 

 such rats on landing may carry and spread the 

 disease amongst rats on shore, which themselves 

 become a focus for plague amongst human beings ; 

 but it would be a serious omission on the part of 

 sanitary officers were they to assume that this is the 

 onlv, or even the chief, mode of importing the disease 

 oversea or from one locality to another. 



Chapter vi. deals with the different views regard- 

 ing the etiology of pandemics and epidemics of 

 plague, views which, with few exceptions, fall within 

 periods antecedent to the discovery of the Bacillus 

 pestis, and attributed a primary causality to in- 

 fluences which we now know to be accessory, 

 though important, circumstances in the dissemination 

 and spread of the disease, as, for instance, famine, 

 scarcity, insanitary disposal of the dead, and others. 



The known variations in diffusive powers of 

 epidemics and the effect of seasonal influences are 

 considered in chapter vii., and are illustrated by 

 charts and diagrams, without, however, bringing us 

 nearer to an explanation of the fact that seasonal 

 influences plav an important part, unless we accept 

 as seriously meant the statement by Gottschlich, 

 according to whom the seasonal periodicity of plague 

 in Egypt is to be e.Kplained by the seasonal breeding 

 period of the rat (p. 15S). 



The variation in virulence of plague epidemics is 

 dealt with in chapter viii., and is illustrated by an 

 account of various epidemics which have occurred 

 in -Astrakhan and Vetlianka, 1877-8; Avignon, 1348; 

 Kathiawar, 1S20; Pali, 1836; Marseilles, 1720; Egypt, 

 1S34, and others. From these the author concludes 

 that not only do epidemics amongst themselves show- 

 great variations in virulence, but that an at first 

 mild epidemic is succeeded by one of great virulence 

 in the same or subsequent years, and further that 

 the various types may be running concurrently in 

 the same locality and at the same time, e.g. at 

 Kathiawar, Pali, Marseilles, Russia, and other places. 

 Tlie often observed fact that glandular swellings 

 without fever may precede or follow plague preva- 

 lence is dwelt upon, without offering for it a satis- 

 factory explanation, beyond the suggestion that 

 variation of virulence may be due to change in viru- 

 lence of the Bacillus pestis with change in the 

 surrounding physical conditions, or to differences in 

 susceptibility of those attacked, such as are brought 

 about by scarcity and famine, poverty, insanitary 

 dwellings, &c. 



The conditions which foster endemicity and epi- 

 demicity are considered in chapter ix. The in- 

 fluence of the various at present existing endemic 

 centres on dissemination of plague to exotic coun- 

 tries, the different conditions (poverty, misery, 

 NO. 1874, VOL. 72] 



deficient food, overcrowding, insanitary dwellings) 

 under which the various peoples have lived and still 

 live, as, for instance, in the Himalayas, in Bombay, 

 Canton, Hong Kong, Cape Town, and others, play 

 an important part in predisposing to plague, " and 

 it is in a population living under these social and 

 local conditions that plague usually commits its 

 greatest ravages " (p. 193). 



The modes of dissemination from one locality into 

 another and within an infected locality are described 

 in chapters x. and xi. respectively. As to the first, 

 illustrations are given that plague travels by the 

 most frequented trade routes, that persons sick with 

 or incubating plague carry infection, so also infected 

 clothes and personal effects ; that infection conveyed 

 to a new centre (infected cargoes and infected rats) 

 may affect rats before human beings; that owing 

 to panic caused by plague breaking out in a given 

 locality, open and secret flight of inhabitants are 

 instrumental in the dissemination of the disease. In 

 the dissemination of plague within an infected 

 locality, importance is attached in the first place to 

 the high infectivity of the pneumonic form of plague, 

 as contrasted with simple bubonic plague, which is 

 not directly infectious. Next stands the infectivity 

 of the septic£emic form; in which the excretions 

 contain the Bacillus pestis, wherefore clothes and rats 

 play an important role. In the conve\'anee of plague 

 from the rat to man, the part that insects — fleas, 

 lice, bugs, ants — play is brought into prominence. 

 In support of this theory, no valid experimental 

 evidence is brought forward ; what there is mentioned 

 is more of the nature of strong belief. It is to be 

 regretted that such prominence is given to this mode 

 of dissemination, seeing that beyond the theoretical 

 possibility, namely, that a blood-sucking insect of a 

 plague-infected animal the blood of which, pre- 

 sumably, contains the Bacillus pestis might be the 

 means of causing by its bite cutaneous inoculation 

 of a new individual, including the human, there is 

 not sufficient evidence that such has actually been 

 observed either naturally or experimentally. All the 

 direct evidence at present available is of a negative 

 character. The numerous modes of conveyance of 

 plague from man to man, from rat to rat, from rat 

 to man and vice versa, which have actually been 

 observed both under natural as also under laboratory 

 conditions (chapter xiii.) are quite sufficient to account 

 for all the facts without ascribing to the flea anv 

 other than a very restricted and accidental role, if 

 any. 



Part iii. deals with plague in the individual. The 

 morbid anatomy and pathology, including histology 

 and distribution of the B. pestis in the different 

 tissues, are described in chapter xii., as also the 

 details of several autopsies of typical plague cases ; 

 whereas chapter xiii. gives an extensive description 

 of the various channels by which an individual may 

 receive the infection — the skin, and hence directly 

 into the lymphatics; the skin, and hence directly 

 into the bloodvessels ; the mucous membranes, par- 

 ticularly of the fauces; the respiratory tract. The 

 author accepts the three-fold grouping of plague in- 

 fection made by the Indian Plague Commission 



