132 GLOSSARY. 



Sphinc'ter (Gr. sphingo, I bind). The name given to certain 

 circular muscles which keep the orifices which they sur- 

 round habitually shut, as the sphincter ant at the distal end 

 of the rectum, the sphincter vesicce (sphincter of the bladder) 

 at the mouth of the bladder, and the sphincter oris (sphincter 

 of the mouth) or orbicular muscle of the mouth. 



Sphyg'mograph. (Gr. sphugmos, the pulse; grapho, I write). 

 An instrument for recording graphically the movements of 

 the pulse. 



Spi'cula (L. splculum, a point). The needle-shaped siliceous 

 bodies found in sponges, &c. 



Spi'culum amo'ris (L. sting of love). A hard pointed body con- 

 tained in a sac connected with the penis in some Odonto- 

 phora, and which is discharged in the act of copulation. 



Spige'lian. A name applied to one of the lobes of the liver, 

 so called from the name of an anatomist. 



Spi'na bi'fida (L. spina, a thorn; bifidus, split into two parts;. 

 An abnormal condition of the sacral part of the vertebral 

 column in which the neural canal is unclosed. 



Spi'nae mentales (L. spines of the chin). Two prominent tuber- 

 cles on the lower jaw-bone to which muscles are attached. 



Spi'nal acces'sory. The eleventh pair of cerebral nerves in the 

 higher Vertebrata, so called because they arise from the 

 sides of the spinal cord. 



Spina'lis cervi'cis (L. spinal of the neck). A small muscle pass- 

 ing from the spines of the posterior cervical vertebrae to 

 the axis. 



Spina'lis dor'si (L. spinal of the back). A long narrow muscle 

 passing from the lumbar to the upper dorsal region of the 

 spinal column. 



Spi'nous (L. spina, a thorn). Applied to the neural spines or 

 spinous processes of the vertebrae ; also to a process of each 

 great wing of the sphenoid bone. 



Spi'racle (L. spiro, I breathe). An aperture which in some 

 Elasmobranch fishes leads into the cavity of the mouth. 



Spiro'meter (L. spiro, I breathe; metron, a measure). An 

 instrument for testing the capacity of the chest. 



Splan'chnic (Gr. splanchna, entrails). The name given to 

 three (great, small, and smallest) sympathetic nerves 

 which supply some of the viscera. 



Splanch'nopleure (Gr. splanchna, entrails ; pleura, side). The 

 layer of the blastoderm from which the viscera are deve- 

 loped. 



