24 On Flukes. 



and was exhibited, by his desire, at the Conservatoire des Arts 

 et Metiers ; he even appointed a commission of scientific men to 

 examine and report upon it, being, as was stated, so pleased 

 with it that he intended to purchase the invention. But, like 

 every preceding attempt, it ended in nothing. 



We have now, as far as our limits would permit, noticed 

 the various sources from which motive power has been, or was 

 expected to be, derived. Every experiment that bears on the 

 subject seems to indicate that all motive power is ultimately 

 reducible to heat, or at least is proportional to it. And, if such 

 be the case, the only useful object for which our experiments 

 can be made, would be to discover the most economical means 

 of obtaining, and the most effectual mode of applying, heat. 

 One important conclusion follows from what has been said, 

 that if it is not absolutely impossible to discover a prime mover 

 which shall supersede steam, success is so difficult, and beset 

 with so many obstacles, that prudence suggests great caution, 

 both in contriving and adopting any principle or machine 

 having this for its object. On the other hand, it is clear that 

 excellent as the steam-engine undoubtedly is, only a small por- 

 tion of the heat required by it is effective in producing motion ; 

 and, therefore, it affords abundant opportunities for ingenuity 

 to distinguish itself, and for enterprise to secure profit, in 

 further perfecting its details. 



ON FLUKES. 



BY T. SPENCEE COBBOLD, M.D., F.L.S., 



Lecturer on Comparative Anatomy, Zoology, and Botany, at the Middlesex 



Hospital Medical College. 



Flukes constitute a numerous group of diminutive beings who 

 enjoy the privilege of snugly ensconcing themselves within 

 the interior of other living animals. That eminent parasi- 

 tologist, Alexander von Nordmann, well expressed the un- 

 pleasing sensations which pervade the human mind when 

 first induced to contemplate the curious variety of creatures 

 destined to inhabit so strange a dwelling. " Who," he 

 exclaims, in the opening section of his valuable Mikrogra- 

 jphische Beitrage, "who that did not witness the fact, could 

 possibly have believed that Nature had formed living animals 

 to grope for their existence in the interior of other beings so 

 advanced in the scale of organization, not only, indeed, in the 

 higher, but even in the highest ! Nevertheless, such is the 

 case. Man shrinks when he first hears of it ; he stands aghast 



