400 ON THE ORIGIN OF ENTOZO\ 



Tt is preposterous to tell us that the germs of the Entozoa (than 

 which nothing is more delicate) are thus preserved for centu- 

 ries, transferred from one generation to another; and it is 

 equally incredible that the germs (in each generation equally 

 exposed to circumstances favourable to their development) 

 should, as it were by choice, select this particular individual 

 for their nidus. 



We know of no means by which the ovules of worms can 

 be carried first into the uterus or ovaries of the female parent, 

 and secondly from thence into the foetus. 



Even supposing that all parasitical worms are produced from 

 eggs, still I cannot conceive any method by which they can be 

 transferred to the uterus or ovary of the female, or from them 

 to the contained foetus or germ. As worms exist in every 

 region of the body, it is indispensable that their eggs should 

 first be absorbed by the lymphatics, thence carried into the 

 veins, pass with the blood through the lungs, and through the 

 arteries, before they can be deposited in the ovary or uterus ; 

 and when (after this perilous journey) they shall have arrived 

 so near the place of their destination, they have to pass through 

 the vessels of the placenta. But throwing out of the question 

 the dangers attendant upon such an expedition, there are two 

 powerful objections to this finely-spun theory ; first, the trunks 

 of the vessels, arterial as well as venous, both those concerned 

 in nutrition and secretion, are attenuated to that degree that 

 they become colourless, and refuse to transmit red globules ; 

 and, secondly, we should have every part of the system 

 abounding with the eggs of worms. 



The first consideration does clearly point out the fallacy of 

 the hypothesis, for globules of blood are infinitely smaller 

 than the eggs of worms, and those vessels which will not 

 transmit the former will undoubtedly reject the latter; and I 

 am not now making the comparison with the eggs of the larger 

 species, such as those of Ascaris lumbricoides, Strongylus 

 gigas, Echinorhynchus , or Tarda, but with those of the 

 smaller species, such as the Distoma trichoccphalus, and such 

 like ; and I am well convinced that no Entozoon could be 

 mentioned, whose eggs would not each be capable of containing 

 many globules of blood. I would now call the attention of the 

 reader to the vessels which by means of their minute radicles 

 absorb the different fluids. Their mouths are invisible to the 



