102 Ctivieriaii System of Zoology, 



it, is truly marvellous. It is this which constitutes the whole 

 vegetative life. 



For the nutrition of solids, we perceive no other arrange- 

 ment than a minute subdivision of the last arterial branches ; 

 but for the production of liquids, the apparatus is more varied, 

 and more complicated. Sometimes these last extremities of 

 the vessels expand simply over large surfaces, from whence the 

 liquid to be produced exhales ; sometimes the liquid exudes 

 from the bottom of little cavities ; more frequently the arterial 

 extremities, before changing into veins, give rise to particular 

 vessels, which carry {transportent) this liquid ; and it is at the 

 point of union of the two kinds of vessels that it appears to be 

 formed. Thus the minute blood-vessels and these peculiar 

 {propres) vessels *, by interlacing, form bodies called conglo- 

 merate, or secretory, glands. 



In animals which have no circulation the nourishing fluid 

 bathes all the parts, each part drawing from the fluid the mole- 

 cules necessary for its support ; if it be required that a peculiar 

 liquid should be formed, proper vessels float in the nourishing 

 fluid, and extract, by their pores, the elements necessary for 

 the composition of this liquid. 



Thus the blood constantly maintains the composition of all 

 the parts, and repairs the alterations which are the continual 

 and necessary consequence of their functions. The general 

 ideas that we are able to form of these operations are suffi- 

 eiently clear, although we have not distinct notions of what 

 takes place in detail in each point ; for want of knowing, wdth 

 sufficient precision, the chemical composition of each part, we 

 cannot give an exact account of the transmutations necessary 

 for its production. There are, also, other glands, which sepa- 

 rate from the blood certain liquids, that are either ejected as 

 superfluous matter, as the urine from the kidneys, or are of 

 some service to the animal, as the ink of the cuttle-fish, and 

 the purple of some of the Mollusca f, &c. The production of 

 a germ, or generation, is an operation, or phenomenon, far more 

 difficult to conceive than the secretions ; we may regard it as 

 almost incomprehensible ; but when once the existence of the 

 germ is admitted, the difficulty is removed. So long as the 

 germ adheres to the mother, it is nourished, as if it were one 

 of her organs ; when once it is detached, it has itself indivi- 

 dual life, which is essentially similar to that of the adult. 



* To these vessels, which Cuvier calls proper, or peculiar, some physio- 

 logists have recently given the name of capillary vessels. 



f The cuttle-fish, when pursued, ejects a black liquor, to darken the 

 water, and hide itself from its enemies. 



