SECT. XXXIX. i. i. GENERATION. 379 



petual circles towards the fide affe&ed, in order to get a more 

 accurate view of objefts ; for the fame reafon as in fquinting 

 the affeded eye is turned away from the object contemplated. 

 Sheep in the warm months keep their nofes clofe to the ground 

 to prevent this fly from ib readily getting into their nodrils. 



The liquor amnii is fecreted into the womb as it is required, 

 not only in refpect to quantity, but, as the digeftive powers of 

 the fetus become formed, this fluid becomes of a different con- 

 fidence and quality, till it is changed for milk after nativity. 

 Haller, Phyfiol V. i. In the egg the white part, which is 

 analogous to the liquor amnii of quadrupeds, confifls of two 

 didinct parts ; one of which is more vifcid, and probably more 

 difficult of digeftion, and more nutritive than the other ; and 

 this latter is ufed in the lad week of incubation. The yolk of 

 the egg is a dill dronger or more nutritive fluid, which is drawn 

 up into the bowels of the chick jud at its exclufion from the 

 fhell, and ferves it for riourifhment for a day or two, till it is 

 able to diged, and has learnt to choofe the harder feeds or grains, 

 which are to afford it fudenance. Nothing analogous to this 

 yolk is found in the fetus of laliferous animals, as the milk is 

 another nutritive fluid ready prepared for the young progeny ; 

 it is alfo a curious circumdance, that the fird milk of female ani- 

 mals after parturition is much thicker, like the yolk of egg, and 

 much more coagulable, than that which is fecreted after a few 

 days, when the digedive powers of the offspring are become 

 ftronger. 



The yolk therefore is not neceffary to the fpawn of fifh, the 

 eggs of infects, or for the feeds of vegetables ; as their embry- 

 ons have probably their food prefented to them as foon ns they 

 are excluded from their (hells, or have extended their roots. 

 Whence it happens that fome infects produce a living progeny 

 in the fpring and fummer, and eggs in the autumn ; and fome 

 vegetables have living roots or buds produced in the place of 

 feeds, as the polygonum viviparum, and magical onions. S^e 

 Botanic Garden, p. ii. art. Anthoxanthum. 



There feems however to be a refervoir of nutriment prepared 

 for fome feeds befides their cotyledons or feed-leaves, which may 

 be fuppofed in fome meafure analogous to the yolk of the egg. 

 Such are faccharine juices of apples, grapes, and other fruits, 

 which fupply nutrition to the feeds after they fall on the ground. 

 And which is the milky juice in the centre of the cocoa-nut, and 

 part of the kernel of it ; the fame I fuppofe of all other monoco- 

 tyledon feeds, as of the palms, graifes, and lilies. The milky 

 juice in the centre of the cocoa-nut feems curioufly to referable 

 the chyle of animals, as it contains oil diffufed with mucilage 



and 



