Book II. ANIMAL ANATOMY. 283 



should likewise be preserved in spirits ; and this, from the small size of these beings, can 

 be done with facility, and will supersede the necessity of any laboured description of the 

 objects themselves. "With such materials, he will find a most important advantage in 

 submitting his doubts and queries to some one of the societies in London, whose object 

 is more particularly the investigation of such matters. The Zoological Club of the Lin- 

 naean Society is composed of the most eminent naturalists in the kingdom ; and their 

 labours promise to effect much in this department of rural economy. Specimens, &c. 

 may be sent to the secretary, N. A. Vigors, Esq., Soho Square, London; or they may 

 be sent to the same gentleman, as secretary of the Zoological Society, Bruton Street, 

 London. 



1842. The classification of animals, until the discoveries of the French philosophers, 

 was long regulated by their external characters alone ; from this resulted all the artificial 

 systems of the last century. A more intimate acquaintance with nature has convinced 

 naturalists of the present day, that it is only by considering the structure of animals, both 

 internal and external, with reference to their modes of life, that the natural system can ever 

 hope to be discovered. The brilliant anatomical and physiological discoveries of Cuvier, 

 Lamark, I-atreille, and others, in France, have laid the foundation of this system ; but it 

 was reserved for our own countryman, Macleay, to generalise their details, and combine 

 these valuable materials into a whole. By a new and most extraordinary mode of 

 investigation, this gifted writer has proved the existence of five primary divisions in the 

 animal world, corresponding to the same number in the vegetable : while, through the 

 doctrine of affinity and analogy, the apparently contradictory opinions of Linnaeus, with 

 those of others who succeeded him, are in many instances reconciled and explained. 

 {Hor. Ent. Trans, of Linn. Society, 14, p. 46.) 



Chap. II. 

 Animal Anatomy. 



1843. The leading organs of animal structure may be conveniently arranged as 

 external and internal. 



Sect. I. External Anatomy of Animals. 



1844. All animals agree in possessing an exterior covering, or skin, to modify their 

 surface, regulate their form, and protect them from the action of surrounding elements. 

 In the more perfect animals, this organ consists of the following parts : the cuticle, the 

 corpus mucosum, the corium, the panniculus, and the cellular web. 



1845. The cuticle is destitute of blood-vessels, nerves, and fibres, and usually consists of a thin transparent 

 membrane possessing little tenacity. In those animals which live on the land, it is more rigid in its 

 texture, and more scaly and dry on its surface, than in those which reside in the water. In aquatic 

 animals, it is in general smooth, often pliable ; and, in many cases, its texture is so soft and delicate, that 

 it appears like mucus. It assumes, likewise, other appearances, such as scales, nails, shells and plates, 

 which deserve the attentive consideration of the naturalist, as furnishing him with important characters 

 for the arrangement of animals. 



1846. The mucous web occurs immediately underneath the cuticle, from which, in general, it may be 

 easily disjoined ; but it is often so closely attached to the true skin below, as not to be separated even by 

 maceration in water. 



1847. The corium {cutis vera), or true skin, lies immediately underneath the cuticle or mucous web. It 

 is usually destitute of colour. It consists in some animals, as quadrupeds, of solid fibres, which cross one 

 another in every possible direction, and form a substance capable of considerable extensibility and elasti- 

 city. It is more obviously organised than the two membranes by which it is covered. Blood-vessels and 

 nerves penetrate its substance, and may be observed forming a very delicate network on its surface. 



1848. The muscular web varies greatly in its appearance according to the motions which the skin and its 

 appendices are destined to perform. It consists of a layer of muscles, the extremities of whose fibres are 

 inserted into the corium externally, and adhere to the body internally in various directions. This layer is 

 very obvious in the hedgehog and the porcupine, to assist in rolling up the body and moving the spines; 

 and, in birds, to effect the erection of their feathers. In man it can scarcely be said to exist, except in the 

 upper parts, where cutaneous muscles may be observed, destined for moving the skin of the face, cheeks, 

 and head. In the skin of the frog, the only cutaneous muscles which can be observed are seated under 

 the throat ; the skin on the other parts of the body being loose and unconnected with the parts beneath. 

 The use of this layer of the integument is to corrugate the skin, and elevate the hairs, feathers or spines 

 with which it is furnished. 



1849. The cellular web forms the innermost layer of the common integuments, and rests immediately 

 on the flesh of the body. It consists of platea crossing one another in different directions, and forming a 

 cellular membrane, varying in its thickness, tenacity, and contents, according to the species. In frogs it 

 does not exist, '^^e cells of this membrane are filled with various substances, according to the nature of 

 the animal. In general they contain fat, as in quadrupeds and birds. In some of these the layer is 

 interrupted, as in the ruminating animals, while it is continuous in others, as the boar and the whale. 

 In birds, while a part of this web is destined for the reception of fat, other portions are receptacles for air. 

 In the moon-fish the contained matter resembles albumen in its chemical characters. 



1850. The appendices of the skin are hairs, feathers, horns, scales, shells, and crusts. 



1851. Hairs differ remarkably not only in their structure, but likewise in their situation. In s6me cases 

 they appear to be merely filamentous prolongations of the cuticle, and subject to all its changes. This is 

 obviously the case with the hair which covers the bodies of many caterpillars, and which separates along 

 with the cuticle, when the animal is said to cast its skin. In true hair the root is in the form of a bulb, 

 taking its rise in a cellular web. Each bulb consists of two parts, an external, which is vascular, and 



