INVEETEBRATA. 5 



of invertebrate animals, and to the mode in which they are accommodated to the 

 numerous forms of their respective bodies, and to the modifications of structure. It 

 would be too presumptive to attempt to point out the functions of the different parts 

 of the brain ; nevertheless, when their intelligence is considered, also their special 

 senses the organs for prehending food and comminuting it, or for taking softer or 

 more fluid kinds, their organs for digesting and assimilating the food, for circulating 

 the blood, and for respiratory changes it seems not unreasonable to conclude, and to 

 attempt to point out, that the preceding attributes, forming a part of the plan of the 

 animal creation, must be perfected by similar centres and nerves, however much they 

 may be modified and contracted, to accord with more simple organs and such 

 diversified bodies. 



The small brain allows the necessary intelligence to be manifested, also sight, and 

 some degree of hearing. It is probable the nervous cord passing on each side of the 

 oesophagus is composed of a voluntary and sensitive tract, also of an involuntary one, 

 which has similar functions to those of the par vagum ; and when combined with the 

 more sensitive quality in the ganglia, may answer all the purposes of the par vagum 

 and sympathetic conjoined. Such a disposition accords with the brain, the oblong 

 medulla and spinal cord of higher classes arranged in a different form of structure. 

 The involuntary and sensitive qualities of the ganglia correspond with those of the 

 spinal ganglia in the highest animals for giving auxiliary respiratory powers to the skin, 

 and therefore in the invertebrate favour the functions of the branchiae, the air-tubes 

 and the viscera. In the highest animals the voluntary impulses proceed from distinct 

 centres in the brain, and are conducted by corresponding tracts ; the force and power 

 of the muscles depend on the cerebellum and the large size of the oblong medulla and 

 spinal cord; and therefore, by analogy, it may be concluded that the large ganglia 

 in the invertebrate exist for supplying also the energy for the continuance of the swift 

 motions in flight or other modes of progression, whilst a very small voluntary centre 

 and tract suffice for the variations of motion such creatures require. 



