on the Equivocal Production of Animals. 395 



organs for the secretion of worms. The liver is appropriated to 

 the formation of bile, and it is a highly improbable supposition to 

 imagine that it is also calculated to secrete living animals. 



If worms were thus fortuitously produced, without any distinct 

 or appropriate glands or organs, and consequently without any 

 mould or matrix to give them a determinate form, how does it hap- 

 pen that no new species are ever seen, or indeed that there should 

 be any regularity or resemblance in their forms at all ? How does 

 it happen that in the ileum, in the very same situation, at the 

 same time, and under similar circumstances, two such distinct spe- 

 cies should be formed as the Tccnia and the Ascaris lumbricoides ? 

 That in the rectum the Oxyuris and Tricocephalus should have a 

 common origin, or that the Distoma hepaticuyn should be found 

 only in the liver and gall ducts ? On the supposition of a direct 

 propagation from parent animals, the peculiar habitats of these dif- 

 fierent species, where they obtain the kind of food, and protection 

 best suited to their natures, can be satisfactorily accounted for. 

 But above all, on this supposition, how does it happen that there 

 is both male and female worms produced ? Why, if there is any 

 sex at all, should not the female be sufficient } Or what laws in 

 the fermentive process, or verminous diatheses, tend to regulate 

 the distribution of the sexes .'' I know it has been observed by some 

 writers on the subject,* that where the Ascaris lumbricoides pre- 

 vail, the females greatly preponderate, and that males are often not 

 to be found at all ; yet I have never found Ascarides exist in con- 

 siderable numbers, either in man or in other animals, without ob- 

 serving both males and females. 



Here it may also be remarked, that a relaxed or diseased condi- 

 tion of the bowels, or a vitiated state of their nutritious contents, 

 are the least likely preparatives or requisites for a creative or con- 

 ceptive process ; for generation implies a healthy and vigorous con- 

 dition, and an active and increased excitement of parts. — not a 

 morbid or deranged structure. The analogy of tumours and ex- 

 cresences growing from various parts of the body, will not serve to 

 elucidate this subject. These are mere extensions or aberrations 

 of the re-productive powers inherent in all animals; but surely 

 very different from the formation of a new being, which is, after a 

 time, capable of an independent existence. 



Another argument against the theory of spontaneous production, 

 is the fact that intestinal worms are furnished with organs of ge- 

 neration, and produce eggs, and even young, in the same manner 

 as other species of the animal creation. In many species, as the 

 Ascaris lumbricoides, there is a male and female worm ; others 

 again, as the Cestoides, are hermaphrodite, and some, as the Tre- 

 matodes, are androgynous. When we examine the female Ascaris 

 lumbricoides, and perceive how large a proportion of the whole 



• Bremser, Cloquet. 



