46 



VIRCHOW, ON TRICHINA SPIRALIS. 



not a trace of the parasites could be discerned, where after- 

 wards they would be found in such great numbers. 



The TrichincB progressively advance into the interior of the 

 muscular fasciculi, where they are often seen, several in a 

 file one after the other. Behind them the muscular tissue 

 becomes atrophied, and around them an irritation is set up, 

 and from the commencement of the fifth week they begin to 

 become encysted. The sarcolemma is thickened, and the 

 contents of the muscular fibres exhibit indications of a more 

 active cell-growth; the cyst consequently is the product of 

 a sort of traumatic irritation. 



In the dog, the development of the Trichinee in the intes- 

 tine may be very readily followed, but they do not pass into 

 the muscles, either because the intestine or the digestive 

 secretions of the dog present obstacles to the migration or to 

 the ulterior development of these worms. 



I have to thank Professor Zencker, of Dresden, for the 

 muscles of the woman with which I began this series of 

 researches. In this case death had occurred under circum- 

 stances precisely similar to those which I observed in my 

 rabbits ; the autopsy disclosed no lesion beyond the presence of 

 innumerable Trichinee in the muscles, and neither here nor in 

 the muscles of the rabbits were they visible to the naked eye. 



From these facts, then, it results, that fatal cases of 

 infection by Trichinee may take place, in which the cause 

 of death cannot be recognised except by the microscope; 

 and that, up to the present time, no other cases had been 

 observed except those in which the entozoa had not only 

 become encysted, but in which the greater number of the 

 cysts had already reached a very advanced stage of cretifica- 

 tion ; for it is in this condition only that they become visible 

 to the naked eye. 



Moreover, since the cysts are not formed before the fourth 

 to the sixth week, nor does the cretification take place, pro- 

 bably, till after the lapse of some months, it may be con- 

 cluded that, up to the present time, cases of this affection 

 have not been recognised in the human subject until it 

 had undergone a sort of cure, the symptoms belonging to 

 the recent evolution of the Trichinee having been long for- 

 gotten. If the antecedent conditions in patients who have 

 experienced the symptoms above cited were accui'ately 

 noted, we should probably soon see the number of cases of 

 trichinization increased. 



Besides the merit of ha\ang proved the existence in 

 man of the Trichinee which I had found in the intestine 

 of the dog, experiments with reference to which I have 



