46 
Ascaris lumbricoides 
VI. Mechanism of protection of the body against the invasion 
of Ascaris larvae. 
Yoshida reports that larvae found in the pleural cavities are surrounded 
by groups of white blood corpuscles and histiocytes (Yoshida, 1919 a , p. 23). 
This is clearly the same phenomenon as the capture of the Ankylostome larvae 
in the lymph glands, two days after infection, as observed by Looss (1911, 
p. 521). This author showed that such larvae were killed by the lymphatic 
cells, and that this process forms part of the mechanism of defence. Strong 
infection stimulates the glands. “It seems as though the larvae were able to 
withstand the attacks of the lymphatic cells for a certain length of time or 
possibly also the lymphatic cells do not at once commence their attacks. 
If the larvae succeed in escaping from the glands within this time they are 
saved, if they do not succeed they fall a prey to the lymphatic cells.” Captured 
larvae were observed in considerable numbers as early as two days after 
infection. In Yoshida’s cases, the reaction occurred as earlv as 20 hours after 
feeding. 
VII. The extent of natural Ascaris infestation of pigs in England 
AND TREATMENT SUGGESTED WITH A VIEW TO THE ERADICATION OF THE 
DISEASE. 
Messrs C. and T. Harris & Co. of Caine, Wiltshire, at my request, very 
kindly undertook the enumeration of pigs found to contain Ascaris in their 
abattoirs. Out of 370 stores, 62 or 16-75 per cent, contained this worm, out 
of 29 sows, 3 or 10-34 per cent, were affected. These figures are very low com¬ 
pared with the American returns of Raffensperger, who found 41-1 per cent, 
affected (Ransom and Foster, 1920, p. 25). To estimate the economic effect 
of the parasite in this country, further statistics of infection from all districts 
are required, and also extensive observations on the relative weight of infected 
and uninfected pigs. The facts given by myself (Stewart, 1918a, p. 203), although 
based on only 83 examinations, suggest the possibility of considerable loss 
from this cause. 
Treatment. Since animals of two months and over appear to be only 
slightly susceptible to infection, it should be possible to free a herd completely 
of the parasite by a routine administration of santonin or oil of chenopodium, 
to all pigs at the ages of one and two months. Whether the adoption of such 
a routine on a large scale should be recommended or not, would depend on 
the results of the investigation suggested above. 
REFERENCES. 
Looss, A. (1911). The Anatomy and life-history of Agchylostoma duodenale Dub. Pt. n. 
Records of the School of Medicine , Cairo. 
Ransom, B. H. and Foster, W. D. (1917). Life-history of Ascaris lumhricoides and related 
forms, Journ. Agric. Research, n, 395. 
