INSECTA.' 225 



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ganglion, gives off, according to him, four pairs of nerves, and 

 each of the following ones, two; so that by counting the eight 

 pairs of the brain, and the ten spinal bridles, which may also 

 be considered as so many pairs of nerves, we shall have in all 

 forty-five pairs, exclusive of the two solitary nerves above- 

 mentioned, or from twelve to fourteen more than are found in 

 the human subject. The two nervous cords which form the 

 ganglions by their union, are tubular amd composed of two 

 tunicks, in the exterior of which we observe tracheae; a me- 

 dullary substance fills the central canal. The admirable work 

 of M. Herold on the anatomy of the larva of the great Papilio 

 brassicas, L., studied throughout its various degrees of devel- 

 opment, and to the period of its transformation into a chry- 

 salis, show^s us that the nervous system and that of the diges- 

 tive organs experience remarkable changes ; that in the be- 

 ginning, the nervous cords are longer and further apart, an 

 observation which strengthens the opinion of one of the greatest 

 zootomists of the age. Doctor Serres, on the origin and devel- 

 opment of the nervous system. In our general remarks on 

 points common to the three classes of articulated animals pro- 

 vided with articulated feet, we mentioned the various opinions 

 of physiologists with respect to the seat of the sense of hearing 

 and of smell. We will merely add, in regard to the former, 

 that the little nervous frontal ganglions of which we have spo- 

 ken, seem to confirm the opinion of those who, like Scarpa, 

 place it in the origin of the antennse. I have detected two 

 small orifices near the eyes of certain Lepidoptera, which, 

 perhaps, are auditory canals. If, in several Insects, particu- 

 larly those furnished with filiform, or long, setaceous antennre, 

 they (the antennse) are organs of touch, it seems to us diflicuit 

 to account for the extraordinary development they acquire 

 in certain families, and more particularly in the males, if we 

 refuse to admit that they are then the seat of smell. The 

 palpi also, in some cases, as when they are greatly dilated at 

 the extremity, may possibly be the principal organs of smell, 

 part of which sense may also perhaps belong to the ligula. 

 The digestive system consists of a preparatory or buccal 

 Vol. III.— 2 D 



