356 Dr. Paris on the Fhysiology of the Egg, [May, 



the albuminous portions * furnish materials for its evolution, 

 while the vitellus is designed to administer support, until its 

 digestive organs can gain sufficient powers to perform their 

 functions, and the beak a degree of firmness adequate to with- 

 stand the hardness of its natural food. " Jpsiuu animal,'' says 

 Pliny, ** ex albo liqnore ovi corporatury cibus ejus in luteo est." 

 The albumina, however, besides the office thus assigned to them, 

 discharge another important duty, that of retaining by their 

 non-ronducting powers the vital temperature of the cicatricula ; 

 the. vitellus also would seem to answer some other purpose, or 

 why should it be necessary to those birds f whose parents so 

 sedulously supply them with nourishment? 



At each end of the egg, a white, shining, semipellucid body 

 is inserted into the capsule of the yelk, which extends into the 

 albumen in which it floats. These bodies, from, their supposed 

 resemblance to hail, have gained the name of chalazcc, or gran- 

 difies, and, from having been formerly regarded as the sperm of 

 the male bird, that o^t reddles, Bellini ;]: supposes that they a?e 

 composed of numerous canals, which open into the amnios, or 

 cicatricula, and send out their roots into the white for the purpose 

 of forming a communication between them. Dr. Monro,§ how- 

 ever, observes, that " if they be canals, they cannot have the 

 least communication with the cavity in which the chick resides 

 at any time, or in any state of the egg, otherwise than as they 

 are both adhering to the membrane of the vitellus, upon which, 

 or within which, no particular fibres, no canals, are stretched to 

 the cicatricula." " The chalazce," says Harvey, ** appear to be 

 the poles of the microcosm, and serve to connect the different 

 parts of the egg, and to retain them in their due position. In 

 addition to such aji office, Derham ingeniously conjectures 

 that, as they divide the yelk into tw^o distinct and unequal 

 hemispheres, they must preserve the cicatricida (let the position 

 of the egg be what it may) in the same situation ; for since the 

 chalazcc are specifically lighter than the white, the yelk is kept 

 buoyant, and the cicatricula, as it resides in the smaller hemi- 

 sphere, will be always uppermost : this, in my opinion, is the 

 true theory of the use of the chalazcc ; for such a structure will 

 not only preserve the cicatricula from the dangers of concussion, 

 but by regulating its distance from the source of heat, it will 

 ensure for it a more completely uniform temperature than could 

 otherwise happen, and which is so essential to the evolution of 



♦ The ingenious experiments of IVIr. Ilatchett seem to show tliat alhUincn is tlie 

 parent fluid from which other animal principles may be derived : he accordingly found 

 that it was convertible into gelatine ax^fibrinc. 



•f- Pigeons, for example, whose crops John Hunter ascertained to secrete a peculiar 

 fluid during the breeding season for the sustenance of their young. 



X Bellini de Motu Cordis, prop. ix. 



§ jMonro. See his works published by his son, Edin. 1781. 



