Human speech : a study in the purposive action of living matter / by N.C. Macnamara.

  • Nottidge Charles Macnamara
Date:
1908
Catalogue details

Licence: In copyright

Credit: Human speech : a study in the purposive action of living matter / by N.C. Macnamara. Source: Wellcome Collection.

    161/318 (page 131)
    and watee-fleas IS] rise from the circumoesophageal connectives; their true centres of origin however, are situated in the lateral parts of the cerebral ganglion. On a level with the mouth each circumoesophageal connective enlarges to form an oesophageal ganglion which gives off two nerves, one to the second antenna, the other to the viscera. The two ganglia are united by a double com- missure. Mr E. H. Burne remarks that the condition ot the antennary nerves in Apns suggests, that the direct origin ol these nerves in the higher Crustacea from the cerebral ganglion, is the result of an anterior concentra- tion of centres originally separate and post-oral in position,! The ganglia of the ventral chain are paired, and connected by transverse and longitudinal fibres They supply motor, and receive sensory nerves from the segments of the body to which they belonca ^he nervous system of these small Crustacea therefore pTb) IT 1 1-gher Annelid: (p. 1-.6) and the larger Crustacea, represented by such animals as the crayfish. ^ ^ The tactile and visual organs of the small Apus cancri- rmis conform m their general outline so closely to those met with in the crayfish, that we may best ilflr to them in connection with this larger Crustacean. The ordinary crayfish (Astaous ilnviatilis) is common to many ot our streams and rivulets ; it is^raieTy mme greenish or brownish colour. The animal, during the mnier months, may be seen walking along the bottom Compt. Anrtomy ^Museum, p. 19.