GLOSSARY 513 



Commensalism (ko men'sal izm), an association of different species of ani- 

 mals in which at least one benefits without injury to the other. 



Commissure (kom'i shobr), a strand of nerve fibers or nerves joining two cen- 

 ters or ganglia. 



Conditioned reflex (kon dish'iind), a reflex action which is modified or estab- 

 lished by previous experience. 



Conductivity (kon'duk tiv'i ti), the power of conducting or of receiving and 

 transmitting. 



Congenital (kon jen'i tal), conditions existing at birth. 



Conjugation (kon job ga'shiin), a temporary union of two individuals with ex- 

 change of nuclear material. 



Copulation (kop fi la'shun), union of genital regions of two individuals during 

 which spermatozoa are transferred from one to the other. 



Corium (ko'ri um), the deeper layer of the skin or dermis. 



Cornea (kor'nea), transparent coat of modified epithelial tissue over the front 

 of the eye. 



Cortex (kor'teks), superficial portion or outer layer, as of the brain or kidney. 



Cranial (cra'jiial), pertaining to the portion of the skull enclosing the brain. 



Cretin (kre'tin), a defective individual due to abnormality of the thyroid 

 gland. 



Cutaneous (ku ta'neus), pertaining to the skin. 



Cuticle (ku'tikl), the outer surface of the skin of many animals. 



Cycloid scale (si'kloid), a scale which is thin and shows concentric lines of 

 growth without serrated margin. 



Cyclosis (siklo'sis), the rotation of the endoplasm of protozoan forms. 



Cyst (sist), an organism enclosed by a resistant wall. 



Cysticercus (sis ti sur'kus), the bladder worm or encysted stage in the life 

 history of the tapeworm. 



Cytology (sitol'o ji), the science that treats of the minute structure of cells. 



Cytopharynx (si to far'inks), channel from surface to endoplasm in Euglena. 



Cytoplasm (si'to plaz'm), the protoplasm of the cell not including the nucleus. 



Dactyl (dak'til), refers to finger. 



Daughter cells (do'ter selz), the two cells resulting from a division of one cell. 



Delamination (delami na'shun), the formation of a new layer of cells parallel 



to the old by the division and migration of cells of the primary germ 



layers. 

 Dendrite (den'drit), a nerve fiber which carries impulses toward the nerve 



cell body. 

 Dermis (dur'mis), same as corium. 

 Dialysis (dial'isis), separation of dissolved materials in crystalloids and 



colloids by means of semipermeable membrane. 

 Diaphragm (di'afram), a muscular partition between the abdominal and 



thoracic cavities in mammals. 

 Diastase (di'astas), the class of enzymes capable of bringing about conversion 



of starches to sugars. 

 Diencephalon (di en sef'alon), a region of the brain just posterior to the 



cerebrum. 

 Differentiation (dif er en shi a'shiin), the formation of special parts, tissues, or 



cells from the primitive unspecialized layers. 

 Diffuse (dif us'), to mix with or to spread through completely and thoroughly 



' another substance. 

 Digestion (di jes'chun), the conversion of complex unabsorbable food materials 



into a form capable of bodily absorption. 

 Dihyhrid (dihi'brid), progeny or offspring of parents differing in two charac- 

 ters. 

 Dominance (dom'inans), a condition in which one of two characters present 



in the individual appears to the exclusion of the other. 



