384 ON THE ORIGIN OF ENTOZOA 



want of resemblance to the former being already conspicuous, 

 argues the fallacy of his opinion. But amongst the innu- 

 merable species of Ascarides known, which of them, in the 

 state of embryosus, does he imagine he could recognize, so as 

 to refer it to this or that species ? He surely cannot be ignorant 

 that the characters he has mentioned as diagnostic of Ascnris 

 lumbricoides (viz. the nodules of the mouth with the inter- 

 vening tubule), are common to the whole of the genus Ascaris, 

 and if he believed that Ascarides could exist in such a cold 

 medium as water (and this too in the month of December,) 

 this knowledge alone should have induced him to regard it as 

 a peculiar worm. But if he had wished to establish the identity 

 of this species, he should have done so by furnishing good 

 descriptions or drawings of it, so that by examining its external 

 features and internal structure, a correct judgment might have 

 been formed of the animal. We should now refer to the remarks 

 which were made by Muller (p. o^^, note) on the Ascaris vermi- 

 cularis of Linnaeus. Leuwenhoeck, Schoeffer, and others, have 

 been led into a similar error with respect to the Distoma 

 hepaticum, when they have contended for the existence of 

 these animals in streams, brooks, &c., for O. F. Muller, a 

 most indefatigable investigator of aquatic animalcules, has 

 detected many Planaria, in such situations, but never any thing 

 like the Liver-Fluke. Nor have these writers ever given any 

 proof of their having seen the true Distoma ; they have merely 

 made the vague statement. 



We are not in the possession of any certain and indubitable 

 facts proving that parasitical worms are generated in water, or 

 in any situation external to the body. The worms of warm- 

 blooded animals cannot live in a low temperature, and there- 

 fore soon die when removed from the animal body. Brireis 

 must have lost sight of this fact, or it may never have occurred 

 to him, since he thinks that the Ascaris lumbricoides of man 

 could support life in cold spring water in the midst of winter, 

 when the temperature of the human body is about 98" Fahren- 

 heit. Such worms can scarcely be transferred to water in a 

 living state, as exposure to the air alone soon destroys them. 

 The Filaria Medinensis, or Guinea worm, indeed, attempts 

 sometimes to leave the body before death, but in its exit it 

 quickly becomes dry and rigid, and perishes ; nor is it possible 

 to protract the life of a ligule for any considerable time when 



