January 24, 1908] 



SCIENCE 



135 



gulfed by phagocytes which destroy and 

 render them innocuous. The discovery of 

 the opsonins in the normal blood and their 

 increase in states of induced immunity to 

 bacterial and other infections, has added 

 greatly to the clearing up of some of the 

 complicated phenomena of the immune 

 state. That many virulent bacteria— an- 

 thrax, chicken cholera, pyocyaneus, staph- 

 ylococci and streptococci, pneumococci and 

 others— exhibit negative chemotoxis, or are 

 ingested far less by phagocytes than aviru- 

 lent strains of the same microorganisms, is 

 an old observation, and it is very enlight- 

 ening to find, as Rosenow has, that virulent 

 strains of pneumococci do not bind opsonin, 

 while avirulent strains do, and extracts 

 prepared from the virulent germs protect 

 avirulent ones from phagocytosis to a great- 

 er degree than extracts of the avirulent 

 pnemnocoeci themselves. Cultivation out- 

 side the body as saprophytes of parasitic 

 and non-phagocytable pneumococci and 

 other bacteria, tends to alter their relation 

 to the opsonins and to phagocytosis. From 

 which it appears that virulence and nega- 

 tive chemotoxis depend upon certain chem- 

 ical states of bacteria, determined by the 

 conditions of their existence, and affecting 

 the nature of their metabolic products, 

 among which last are substances that are 

 antagonistic to the functioning of the op- 

 sonins. Far as we still are from a clear 

 and full conception of the distinction be- 

 tween virulence and avirulence in bacteria, 

 we must nevertheless welcome this concrete 

 fact as in itself a great gain. 



The body infected with bacteria or other 

 pathogenic microorganisms, although it sur- 

 vive the infection, may not be rendered 

 more resistant; it may be rendered more 

 susceptible to reinfection — that is, it may 

 be sensitized to the infecting agent or its 

 poisonous products. The state of hyper- 

 sensibility, or anaphalaxis, the converse of 

 that of immunity, has been studied with 



energy and profit during the last two years. 

 Perhaps the best known example is the ab- 

 normal reaction developed when an animal 

 infected with tubercle bacilli is injected 

 with the prodiTcts of the growth of the 

 bacillus. Blood serum contains a sub- 

 stance, or substances, which under suitable 

 conditions develop a reaction of this char- 

 acter. That the human organism reacts 

 more vigorously to second and subsequent 

 injections of horse serum than to the first 

 injection is shown by the reports of many 

 instances in which these stronger effects 

 were noted after administering diphtheria 

 antitoxin. It appears that the reaction of 

 hypersensibility depends for its expression 

 upon the existence in the sensitized body of 

 a substance of the nature of an antibody 

 comparable to, but doubtless differing 

 mdely from, the antibodies which are de- 

 veloped during the process of immunization 

 proper to bacterial and other cells. In the 

 case of hypersensitiveness to serum a sec- 

 ond injection, in such small animals as the 

 guinea-pig, may result fatally in a few 

 minutes or after several hours; but should 

 it not so result, the animals have been 

 robbed of their sensitive or anaphalactic 

 state and been rendered "immune" to 

 horse serum in the usual sense, or antian- 

 aphalaetic. These superficial facts suffice, 

 in a way, to indicate that the antibodies 

 governing the anaphalactic state differ 

 from those governing the immune state, 

 and it is, therefore, interesting to learn 

 that they differ further in failing to give 

 the Bordet-Gengou reaction of complement- 

 deviation. 



Studies in immunity pursued during the 

 past several years have tended to show that 

 it may be general to the body or more 

 marked in one part than in another. Hence 

 we have to distinguish a state of ' ' general ' ' 

 and a state of "local" immunity; and it 

 would appear, also, that the whole body 

 may be sensitized or that sensitization may 



