The development of the human body; a manual of human embryology . poglossal has been seen to correspond to certain pri-marily postcranial metameres (p. 192), and its relation to struc-tures taking part in the formation of an organ belonging to theanterior part of the pharynx seems somewhat anomalous. Itmay be supposed that in the evolution of the tongue the ex-trinsic muscles, together with a certain amount of the lingualis,have grown into the tongue thickenings from regions situatedmuch further back, for the most part from behind the lastbranchial arch. Such an invasion of the tongue by muscl
The development of the human body; a manual of human embryology . poglossal has been seen to correspond to certain pri-marily postcranial metameres (p. 192), and its relation to struc-tures taking part in the formation of an organ belonging to theanterior part of the pharynx seems somewhat anomalous. Itmay be supposed that in the evolution of the tongue the ex-trinsic muscles, together with a certain amount of the lingualis,have grown into the tongue thickenings from regions situatedmuch further back, for the most part from behind the lastbranchial arch. Such an invasion of the tongue by muscles from posterior Fig. 161.—The Floor of thePharynx op an Embryo ofabout 20 MM. ep, Epiglottis; fc, foramen caecum;tl and t2, median and lateral por-tions of the tongue.—(His.) 3o8 THE DEVELOPMENT OF THE HUMAN BODY. segments would explain the distribution of its sensory anterior portion, from its position, would naturally be sup-plied by branches from the fifth and seventh nerves, while theposterior portion might be expected to be supplied by the. Fig. 162.—Diagram of the Distribution of the Sensory Nerves op the area supplied by the fifth (and seventh) nerve is indicated by the transverse lines; that of the ninth by the oblique lines; and that of the tenth by the small circles.—(Zander.) seventh. There seems, however, to have been a dislocationforward, if it may be so expressed, of the mucous membrane,the sensory distribution of the ninth nerve extending forwardupon the posterior part of the anterior portion of the tongue, THE SALIVARY GLANDS. 309 while a considerable portion of the posterior portion is suppliedby the tenth nerve. The distribution of the sensory fibers ofthe facial is probably confined entirely to the anterior portion,though further information is needed to determine the exactdistribution of both the motor and sensory fibers of this nerve inthe tongue. The Development of the Salivary Glands.—In embryosof about 8 mm. a slight fur
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