. XXXIX. 6. GENERATION. 585 



both before and after impregnation ; as it is proba- 

 ble, fomething valuable on this fubject might be 

 learnt from them. The latter circumftancc, or that 

 of deficiency of original nutriment, may be deduced 

 from reverfe analogy. 



There are, however, other kinds of monftrcus 

 births, which neither depend on deficiency of parts, 

 or fupernumerary ones ; nor are owing to the con- 

 junction of animals of different fpecies ; but which 

 appear to be new conformations, or new difpofiii- 

 ons of parts in refpeft to each other, and which, like 

 the variation of colours and forms of our domefti- 

 catecl animals, and probably the fexual parts of all 

 animals, may depend on the imagination of the male 

 parent, which we now come to confider. 



VI. i. The nice actions of the extremities of our- 

 Carious glands are exhibited in their various pro* 

 duclions, which are believed to be made by the 

 gland, and not previoufly to exift as fuch in the 

 blood. Thus the glands, which conftitute the liver, 

 make bile ; thole of the ftomach make gaftric acid ; 

 thofc beneath the jaw, faliva; thofe of the ears, 

 ear-wax, and the like. Every kind of gland muft 

 poffefs a peculiar irritability, and probably a 

 i'enfibiliiy, at the early fiate of its exigence ; and 

 in eft be furnifhed with a nerve of fenfe, or of mo- 

 tion, to perceive, and to felecl, and to combine 

 the particles, which compofe the fluid it fecretes. 

 And this nerve of fenfc which perceives the differ- 

 ent articles which compofe the blood, muft at leaft 

 be conceived to be as fine and fubtle an organ, as 

 the opiic or auditory nerve, which perceive light or 

 fo'irid. See Sea. XIV. 9. 



But in nothing is this nice action of the extremi- 

 of the blood-veffels fo wonderful, as in the pro- 

 duction of contagious matter. A fmall drop of 

 variolous contagion diffufed in the blood, or per- 

 haps only by being inferted beneath the cuticle, 



after 



