33 On Medical Entomology, 



internal and external organization seems to remove them 

 from ail other insects except the monoculi, to which they 

 have a great affinitv. On this account several naturalists 

 have united these two genera under the name of Crustacea. 

 But was it necessary to nuke o*" thcni a separate class, and 

 vt-ill naturalists never become sensible of the inconvenience 

 of those endless divisions which render zoalogy an inexpli- 

 cable chaos ? 



Crabs have a head and breast confounded in one piece^ 

 which bears five pair of legs, the first of which terminate 

 generally in pincers. The tail is of greater or less size, and 

 formed of dilfcrent articulations ; their eyes are compound- 

 ed, and supported by a moveable pedicle : they have for tht;. 

 most part four antennas formed of threads, sometimes 

 double or treble : the branchi^ are very complex : they 

 have a muscular heart, from which proceed a great many 

 Vessels ; a stomach supjxjrted by an osseous structure, and 

 containing three hard stony pieces, which pound their 

 aliments. The organs of generation are double in each, 

 sex, and have their exit at the bottom of one of the paira 

 of legs. 



All crabs are aquatic, and change their shell every year ; 

 at the same time also they throw up the stones from thei? 

 stomach*. 



The cray-fisb {Cancel- astacus) U commonly served up at 

 our tables. 



The great horse crab {Cancer pagurus), the lobster {Can- 

 cer gammarus), the prawn {Cancer serratns), the whkte 

 shrimp {Cancer squiUa), and the spiny lobster {Cancer 

 homarus), have a more delicate taste. They all furnish an 

 abundant quantity of gelatine, which renders broth nutritive 

 and detergent. It is by the first of these properties that it 

 acts in phthisis : it develops the second in cutaneous dis- 

 eases, and Pinel recommends it in leprosy f. lam of opi- 

 nion with Bichat, that, notwithstanding the sarcasms 

 sometimes just thrown out against the humoral medicine, it 

 rests ou a real foundation ; and that in a multitude of cases 

 every thing ought to be referred to a vitiated state of the 

 humours J. 



At the period when the cray-fish casts its shell, to 

 assume a new one, there are found on the sides of its 

 stomach, between the membranes of that viscus, two cal- 

 careous concretions, which are employed as absorbents, 



• Cuvier Tab. Element, de I'Hist. Nat. des Anhn- p. 456. 

 f Nosogr. Philos. deux. edit. n.8J8. 

 i Anat. Gener. part I. p. 25C< 



under 



