108 
Cruce 
Figure 1. High contrast photographs of 30/a thick sections of lizard spinal cord stained by 
the Nissl method. Boundaries of different cellular regions are indicated by dashed lines. 
These were determined by using the criteria of Rexed j.nd studying the sections under 
high magnification. Roman numerals indicate the different cellular regions or “laminae.” 
Representative sections shown are (A) middle of brachial enlargement; (B) thoracic 
level; (C) middle of lumbar enlargement; (D) caudal level. The medial longitudinal fas- 
ciculus (MLF) is a spinal continuation of the brainstem pathway of that same name. 
Reproduced from Cruce (1975), Brain, Behavior, and Evolution, with permission of the 
publisher. 
