GLOSSARY 



483 



HUMORAL SYSTEM - body fluids carrying 

 specific chemical substances which may 

 circulate in formed channels (blood ves- 

 sels or lymphatics) or diffuse freely in the 

 body cavities or tissue spaces, (e. g. , 

 neurohumors of Parker which act on the 

 pigmentary system). 



HYBRID - a successful cross between different 

 species, although organism may be sterile 

 (e. g. , mule). 



HYBRIDIZATION - fertilization of an egg by 

 sperm of a different species. 



HYDRODYNAMICS - process by which the de- 

 tailed architecture of the blood vessels is 

 derived, such details as size, angles or 

 branching, courses to be followed, etc. 

 The internal water pressure may be the 

 cause of specific developmental procedure. 



HYALOPLASM - ground substance of the cell 

 apart from the contained bodies. 



HYPERINNERVATION - supplying an organ 



with more than a single (normal) nerve fiber. 



HYPERMETAMORPHOSIS - protracted and com- 

 plete metamorphosis. 



HYPERMORPHOSIS - overstepping previous on- 

 togenies, though harmonious. 



HYPERPLASIA - overgrowth; abnormal or un- 

 usual increase in elements composing a 

 part. 



HYPERTROPHY - increase in size due to in- 

 crease in demands upon the part concerned. 



HYPERTROPHY, COMPENSATORY - increase 

 in size of part or a whole organ due to the 

 loss or removal of part or the whole of an 

 organ (generally hypertrophy in one mem- 

 ber of the pair of organs). 



HYPOMORPHIC - cells or tissues which are 



subordinate to formative processes (Heid- 

 enhain). 



HYPOMORPHOSIS - harmonious underdevelop- 

 ment. 



HYPOPHYSIS - an ectodermally derived solid 

 (an-iphibia) or tubuler (chick) structure 

 arising anterior to the stomodeum and 

 growing inwardly toward the infundibulum 

 to give rise to the anterior and intermed- 

 iate parts of the pituitary gland. Syn. , 

 Rathke's pocket (chick). 



HYPOPLASIA - undergrowth or deficiency in 

 the elements composing a part. 



HYPOTHESIS - a complemental supposition; a 

 presumption based on fragmentary but sug- 

 gestive data offered to bridge a gap in in- 

 complete knowledge of the facts. May even 

 be offered as an explanation of facts un- 

 proven, to be used as a basis of expecta- 

 tions to be subject to verification or dis- 

 proof. 



HYPOTHESIS, WORKING - an attempt to find an 

 answer to some feature of a complete bio- 

 logical situation by utilizing accepted phys- 

 ical and chemical principles. 



HYSTEROTELY - formation of a structure is 

 relatively delayed. 



IDIOPLASM - equivalent to germ plasm of Weis- 

 mann. Dissimilar determinant units of 

 self-differentiating capacity (genes) each 

 representing some part or character of the 

 organism arranged in some plan comparable 

 to the future arrangement of organic parts 

 (Weismann). 

 IMPLANT - tissue or organ removed to an ab- 

 normal position; graft. 

 IMPLANTATION - process of adding, superim- 

 posing, or placing a graft (or a chemical 

 fraction thereof) within a host without re- 

 moval of anything from the host. Implants 

 may be into the body cavity or into the or- 

 bital or anterior eye chamber cavities. 

 INCOMPATIBILITY - opposed to affinity; tend- 

 ency of cells or cell groups to repel each 

 other when removed from their normal en- 

 vironment. May be expressed in terms of 

 cytolysis or histolysis of one of the cells 

 or groups of cells. 

 INDIVIDUATION - assimilative induction con- 

 cerned with regional character of the struc- 

 ture derived in response to (living) organizer 

 activity; opposed to evocational responses. 

 Refers to process in different regions as 

 affected by the organizer, not by a single 

 chemical substance such as an evocator. 

 Regional nature affected by host environ- 

 ment. 

 INDUCTION - causing cells to form an embry- 

 onic structure which neither the inductor 

 nor the reacting cells would form if not 

 combined; the calling forth of a morpho- 

 genetic functional state in a competent 

 blastema as a result of contact. In con- 

 trast with evocation, induction is succes- 

 sive, and purposeful in the sense that one 

 structure leads to another. Sometimes 

 loosely used to include evocator influences 

 from non-living materials. Originally 

 meant diversion of development from epi- 

 dermis toward nneduUary plate (Marx, 1925). 

 INDUCTION, ASSIMILATIVE - transformation 

 of one presumptive area into a different 

 direction under the influence of inductive 

 forces (Spemann). 

 INDUCTION, AUTONOMOUS - if the inducing 

 implant and the host do not cooperate to 

 form an harmonious whole, the material of 

 the implant may not be used although the 

 inductive forces are unimpaired. The in- 

 ductor takes no part in the inducted struc- 

 ture (e.g., all chemical inductions). Op- 

 posed to complementary induction. 

 INDUCTION CAPACITY - organizational capac- 

 ity; acquired with age and subsequently lost. 

 INDUCTION, COMPLEMENTARY - when the in- 

 ductor, using some of its own material, 

 completes itself out of the reacting system 

 (host material); (e.g., when pr esumptive 

 epidermis is transplanted to presumptive 

 brain region and the embryo completes it- 

 self out of the transplanted material). Op- 

 posed to autonomous induction. 



