158 ON ASSIMILATION AND NUTRITION. 



empioy, and imbibe by the skin and lungs, has been seen to collect in crystals 

 upon their faces. 



Hence, too, the various smells that are emitted from the surface of other 

 animals, arid especially that of musk, which is one of the most common. 

 We trace this issuing generally from the bodies of many of the ape species, and 

 especially the simia^'acc/ms; still more profusely from the opossum, and occa- 

 sionally from hedgehogs, water-rats, hares, serpents, and crocodiles. The 

 odour of civet is the production of the civet-cat alone, the viverra zibetha, 

 and viverra civetta of Linnaeus ; though we meet with faint traces of it in 

 some varieties of the domestic cat, the felis catta of the same wrjter. Ge- 

 nuine castor is, in like manner, a secretion of the castor fiber; but the sus 

 Tajassu, and various other species of swine, yield a smell that makes an. ap- 

 proach towards it. 



Among insects, however, these odours are considerably more varied, as well 

 as considerably more pleasant ; for the musk-scent of the cerambix moschatus, 

 the apis fragrans, and the tipula moschifera, is far more delicate than that of 

 the musk quadrupeds ; while the cerambix suaveolens, and several species of 

 the ichneumon, yield the sweetest perfume of the rose ; and the petiolated 

 sphex a balsamic ether highly fragrant, but peculiar to itself. Yet insects, 

 like other classes of animals, furnish instances of disagreeable and even 

 disgusting scents, as well as of those that are fragrant. Thus, several 

 species of the melitae breathe an essence of garlic or onions ; the staphilinus 

 brunipes has a stench intolerably fetid, though combined with. the perfume of 

 spices ; while the caterpillars of almost all the hymenoptera, and the larves 

 of various other orders, emit an exhalation in many instances excessively 

 pungent. The carabus crepitans, and sclopeta of Fabricius, pour forth a simi- 

 lar vapour, accompanied with a strange crackling 1 sound. 



The odorous secretions belonging to the vegetable tribes are well known 

 to be still more variable ; sometimes poured forth from the leaves of the 

 plant, as in the bay, sweet-briar, and heliotrope ; sometimes from the trunk, 

 as in the pines and junipers ; but more generally from the corol. It is from 

 the minute family of the jungermannia, nearly related to the mosses, and 

 often scarcely visible to the eye, that we derive the chief sense of that de- 

 lightful, fragrance perceptible after a shower, and especially at even-tide :* 

 and from the florets of the elegant anthoxanthum odoratum, or spring-grass, 

 that we are chiefly furnished with the sweet and fragrant scent of new-mown 

 hay. But occasionally the odours thus secreted are as intolerable as any that 

 are emitted from the animal world ; of which the ferula asafatida, or asa- 

 fetida plant, and the stapelia hirsuta, or carrion-flower, are sufficient examples. 



To the same secernent powers, moreover, of animals and vegetables, ex- 

 isting in particular organs rather than extended through the system gene- 

 rally, we are indebted for a variety of very valuable materials in trade and 

 diet, as gums, resins, wax, fat, oils, spermaceti. And to the same cause we 

 owe, also, the production of a multiplicity of poisons and other deleterious 

 substances : such, for instance, as the poison of venomous serpents, which is 

 found to consist of a genuine gum, and is the only gum known to be secreted 

 by animal organs ; the electric gas of the gymnotus electricus and raia tor- 

 pedo ; the pungent sting of the stinging-nettle, urtica urcns, and of the bee, 

 both which are produced from a structure of a similar kind ; for every acu- 

 leus or stinging point of the nettle is a minute and highly irritable duct, that 

 leads to a minute and highly irritable bulb, filled with a minute drop of very 

 acrid fluid : and hence, whenever any substance presses against any of the 

 aculei or stinging points of the plant, the impression is communicated to the 

 bulb, which instantaneously contracts, and throws forth the minute drop of 

 acrid fluid through the ducts upon the substance that touches them. 



As the secernent system thus evidently allots particular organs for the 

 accretion of particular materials, the absorbent system is in like manner only 

 capable of imbibing and introducing into the general frame particular mate- 



* Hooker's Monography of British Jungerm 



