128 Anali/tical Notices of Books. 



Brachia, their functions frequently resembling rather those of 

 arms. The parts composing the three segments of the thorax are 

 minutely described, and their internal processes are especially 

 attended to. The structure, forms, and areas of the wings, their 

 appendages and modifications ; the legs, their articulations and 

 locations, and the parts of the tarsi, are also treated of in detail. 

 This portion of the work furnishes indeed in every respect by far 

 the most complete view, both general and partial, of the external 

 anatomy of insects that has ever appeared. 



The Letters on the Internal Anatomy and Physiology are de- 

 Toted in succession to the systems of Sensation, Respiration, Cir- 

 culation, Digestion, Secretion, Reproduction, and Motion. Each 

 of these presents too vast a field to be touched on by us ; but we 

 cannot refrain from noticing the opinion advanced by Messrs. 

 Kirby and Spence, that the nervous system of insects is of a 

 mixed kind, combining in itself both the cerebro-spinal and the 

 ganglionic systems. On the external resemblance borne by their 

 first ganglion to the brain in vertebrated animals it must be con- 

 fessed that too much stress ought not to be laid; but their capa- 

 bility of domestication and of education, or in other words of 

 acquiring habits not instinctive, their memory, and their possession 

 of that degree of intellect and judgment which enables them to 

 profit by the notices of their senses, appear to us, as to our authors, 

 to furnish so many convincing proofs of the necessity of a common 

 nervous centre. The recent anatomical discoveries of Miiller, 

 which will be noticed in our next number, are also adapted to 

 illustrate and support, in a very striking and unexpected manner, 

 the opinion just alluded to. 



At first sight the subject of the Letter on the Diseases of 

 Insects may appear to partake of the ludicrous. They are how- 

 ever at times annoying to man, those of bees and silk-worms being 

 occasionally extremely detrimental to their proprietor, and the 

 hopes of the aurelian in his choicest larvae being frequently 

 blighted by them. Unfortunately the healing art has yet efi'ected 

 little to remedy them. Their history is in many respects interest- 

 ing, and the descriptions of various malformations and deformities 

 are particularly curious. 



