APPENDIX III 371 



HYP, HYPO (G. hypo, under, below), a prefix in hypoglossal, hypophysis, 

 hypo-secretion. 



HYPAXiAL (G. hypo, plus axis), see epaxial. 



HYPER (G. over, above), a prefix, hyperpharyngeai, hyper-secretion. 



HYPERTROPHY (G. hypcr, plus trcpho, nourish), an overgrowth of an organ 

 or structure. See atrophy. 



HYPOMERE (G. hypo, plus meros, a part), the ventral part of the primi- 

 tive mesodermal somite, giving rise to the somatopleure and splanch- 

 nopleure. See epimere. 



HYPOPHYSIS (G. hypo, plus phyo, to grow), a ventral outpocketing; spe- 

 cifically, the ventral evagination of the diencephalon which meets 

 Rathke's pouch from the stomodeum, the two developing into the 

 pituitary gland. 



Hyracoidea (G. hyrax, a shrew-mouse), an order of mammals, the ''con- 

 ies", including the type genus Hyrax. 



ICHTHY (G. ichthys, a fish), a combining form, as ichthyology, Pter- 



ichthys. 

 IcHTHYOPSiDA (G. ichthys, plus opsis, appearance), vertebrates which 



resemble fish, the fishes and amphibia. 

 IcHTHYOSAURS (G. ichthys, plus saurus, lizard), an order of extinct, aquatic 



reptiles. 

 IGNEOUS (L; ignis, fire), formed through the action of heat; igneous rocks 



are consolidated from a molten state. Those which solidify at the 



surface are volcanic. 

 ILEUM (G. eilo, to twist), the posterior portion of the small intestine, 



meeting the large intestine at the ileo-coHc juncture. 

 ILIUM (L. flank), a bone of the pelvis. 

 ixciDO (L. to cut into), incisure, incisor. 



IXFUNDIBULUM (L. a funnel), the stalk by which the pituitary is at- 

 tached to the brain. 

 INGUINAL (L. iiiguin, groin), pertaining to the groin; the inguinal region, 



or inguinal canal. The mammalian testicles descend through the 



inguinal "canals to the scrotum. 

 INTEGUMENT (L. iutego, to cover), the skin of a vertebrate and its 



derivatives. 

 INTER (L. between), prefix; intercostal, intervertebral. 

 INTRA (L. within), prefix, intracellular. 



1NV.\GINATI0N (L. in, in to, plus vagina, a sheath), an inpocketing or fold- 

 ing in of a structure; as, the invagination of the vegetal pole of a 



blastula to form the gastrula. 

 ISO (G. isos, equal), a prefix implying equal degree; as isotonic, isogamy. 

 ITER (L. a passage) ; specifically, the ventricle of the midbrain, which 



in the mammals is a narrow tube between larger ventricles. 



JEJUNUM (L. jejunus, hungry-), that portion of the small intestine of the 



mammal, extending from the duodenum to the ileum. 

 JOINT (L. junctus, from jungo, to join), an articulation between two 



bones, the structure of the joint limiting the motion between the 



parts. 

 JUGAL (L. jugum, a yoke), a bone of the skull assisting in the formation 



of the zygomatic arch. 



