THE FOREBRAIN OF THE ALLIGATOR 361 
DeLange (’13); but the writer knows too little of their relation- 
ships or significance at present to discuss them. 
Hypothalamus. The hypothalamus of the alligator is highly 
developed. An examination of figures 11 and 12 will show 
that a number of cell groups are present. In his 1913 paper 
DeLange has named these different groups. No attempt has been 
made to do so in the present paper because of a lack of knowledge 
of the fiber connections of the different groups. 
FIBER CONNECTIONS 
With the foregoing descriptions of the cell groups as a basis, 
attention can now be turned to the courses and terminations 
of such of the fiber tracts as have been worked out. Papers 
published by C. L. Herrick, Edinger, Adolf Meyer, Kappers, 
Unger, DeLange, and Johnston contain descriptions of the fiber 
connections of the reptilian brain. These descriptions in al- 
most every case, have been based on adult material, the work 
being done with Weigert preparations which bring out the myelin 
sheaths. On the other hand, the work for this paper has been 
done chiefly with Cajal and Golgi material, which bring out the 
unmyelinated fibers and, in many cases, the axis cylinders of 
the myelinated ones. Repeated attempts to prepare a series 
stained by the Weigert method were not successful so far as the 
forebrain was concerned. These failures, of course, may have 
been due to faulty technique, but only extremely young mate- 
rial was available and in such material many of the myelin 
sheaths may not have become mature. C. J. Herrick (’10) 
has figured on pages 537, 539, and 541 some cross sections of 
the forebrain and the thalamus of Alligator mississippiensis 
showing the fiber tracts and the positions of some of the centers. 
These drawings were made from Cajal material and were of 
much help. A series stained with Ehrlich’s haematoxylin and 
an imperfect series prepared by the Leuden van Heumen method 
were used to check the results obtained by the Cajal methcd. 
