A V 



VERTICAL SECTION THROUGH THE HEAD AND TRUNK 

 OF THE HUMAN BODY 



SK, the skull; CH, the cerebral hemispheres ot the brain; C C, 

 the corpus callosum, a bridge ot nerve-fibres binding the cerebral 

 hemispheres together; CBL, the cerebellum. SP C, the spinal 

 cord; N SP, neural spines ot the vertebra;; C M, a centrum or 

 body of a vertebra ; S, the sacral vertebrae fused ; C, the coccyx, a 

 fusion ol post-sacral vertebrae; A V, intestine and other ab- 

 dominal viscera; L, the liver; M, the muscular midriff or dia- 

 phragm, separating the abdominal cavity from the chest cavity; 

 H. the heart; LU, the lung; ST. the sternum or breastbone; G, 

 the gullet or oesophagus. From a specimen. 



N 



SH 



MU 



A SINGLE NERVE-CELL OR NEURONE 



(Alter Stdhr.) 



N is the nucleus of the cell; NC, the central- 

 sell-substance or cytoplasm. The nerve-cell 

 communicates with others by means ol fine 

 protoplasmic branches or dendrites (D). It 

 gives off a nerve-fibre (XF) to a muscle 

 (MU). This fibre has as its essential part an 

 axis cylinder or core, surrounded by a medul- 

 lary sheath (SH) ot a tatty material; and out- 

 side this there is a clear membrane called the 

 neurilemma. It will be observed that the 

 medullary sheath is not developed at the 

 origin or at the end ol the nerve-fibre. A 

 lateral branch ot the fibre is shown (L B) and 

 the ending (N E) on the muscle. 



