ItoEUAEY 8, 1907] 



SCIENCE 



207 



naturally result from the presence of for- 

 eign bodies in that organ. 



The migrations of smaller forms, even 

 though they may be numerous, are not ac- 

 companied ordinarily by the same effects as 

 those of larger species, since the orifices 

 they make are sufficiently minute to close 

 immediately after the animal and prevent 

 the secondary effects which are due to such 

 abnormal connections. Thus the minute 

 embryo of tapeworms migrate from the 

 alimentary canal to the point of encystment 

 without influencing appreciably the host, 

 and other larvae migrate through the tissues 

 with such little disturbance that unless the 

 numbers be large the host suffers no incon- 

 venience. 



Emphasis should be laid upon the ex- 

 treme importance in the economy of the 

 host which the secondary effects exert. 

 The abrasion and destruction of surfaces 

 and cells and the opening of abnormal com- 

 munications is not per se of such vital im- 

 portance as the results which may follow 

 through the admission of bacteria from the 

 canal into the blood and tissues of the ani- 

 mal. It is frequently held that the unin- 

 jured mucous surface is resistant to the 

 action of bacteria and that typhoid and 

 cholera germs must depend to some extent 

 upon diminished resistance, functional or 

 structural, for their original introduction 

 into the tissues of the body. It is certainly 

 true that many pathogenic organisms exist 

 in the alimentary canal without detriment 

 to the host animal, although if permitted 

 to pass into other parts of the body they 

 excite immediately dangerous symptoms. 

 The perforations of the intestinal wall by 

 Ascaris and the escape of such organisms 

 into the body cavity gives at once the con- 

 ditions for a serious if not fatal peritonitis, 

 and Ascaris is not alone in this respect.^ 



'Piana was the first to note that the migration 

 of Cysticereiis pisiformis into the liver of the 



Examples of this can be multiplied, but 

 one wiU sulfice. In the etiology of appen- 

 dicitis certain factors are regarded as pre- 

 disposing, others are direct causes of this 

 malady. As early as 1724 Santorini re- 

 corded the presence of worms, probably 

 Trichuris, in the appendix. Numerous 

 later authors found at necropsies Ascaris 

 and trichurids in this organ, as well as cal- 

 culi containing eggs of Ascaris and 

 Oxyurias. In 1901 Metehnikoff noted that 

 in several persons who manifested symp- 

 toms of appendicitis when microscopical 

 examination of the feces demonstrated the 

 eggs of Ascaris and of Trichuris, the 

 administration of a vermifuge effected a 

 cure. He maintained that nematodes were 

 the cause of many cases of this disease and 

 explained the role of the parasites as first 

 a direct mechanical or chemical action on 

 the appendix and second an indirect action 

 by the introduction of microbes into the 

 mucosa. Metehnikoff did not commit the 

 error attributed to him by some authors of 

 regarding all cases of appendicitis as of 

 parasitic origin, but specifically stated that 

 there are certainly appendieites of different 

 origin. Subsequent authors furnished ad- 

 ditional evidence of the direct or indirect 

 action of parasites in producing appendi- 

 citis, while others, though admitting the 

 possibility that nematodes may inoculate 

 the intestinal mucosa with bacteria, re- 

 garded this as an inappreciable factor in 



rabbit could introduce bacteria. In two cases of 

 tubercular peritonitis of dog associated with 

 Dioctophyme renale in the abdominal cavity Galli 

 Valerio advanced the view that migration of the 

 nematode made possible the development of the 

 bacillus or carried it into cavity. It has recently 

 been clearly shown that the pin worm, Oxyurias, 

 has burrowed into the wall of the canal and pro- 

 duced there microscopic ulcerations, while it seems 

 probable that it has actually made its way 

 through the wall into the cavity of the pelvis. 

 This perforating action places Oxyurias also in 

 the ranks of parasitic introducers of bacteria. 



