136 PECK. 
EXPLANATION OF PLATE VIII. 
The dissections are all drawn to a scale. 
Fic. 1. Five caudal vertebrae. The letters s,-s, indicate the intervertebral spaces. 
The letters ,-7, denote the nerves as far as they occur in the spaces. ¢, the 
coccyx. 
Fic. 2. Six free caudal vertebree. Letters as before, showing the addition of 
another vertebra, and so of s,, with the corresponding addition of 7;. 
Fic. 3. Seven free caudal vertebrze,— with corresponding addition of s,, followed 
by the occurrence of another pair of nerves, 7. 
Fic. 4. A fan-tail with eight free caudal vertebrze, increasing the intervertebral 
spaces by 5s, ; another pair of nerves now found in space seven. 
Fic. 5. Showing the ordinary number of six vertebrae, and spaces s,-s, (compare 
with Fig. 2), but the usual number of nerves is increased to 7., which does not occur 
in Fig. 2. A similar variation might be indicated for Fig. 3 with its seven vertebrze. 
The sections, except Fig. 6, were drawn with an Abbé camera, Zeiss objective A, 
and ocular 2. 
Fic. 6. A section of the filum terminale taken very near its extremity in the 
coccyx. /.m., the pia mater investment; /., the lumen surrounded by nuclei; 4.v., the 
blood-vessel. This section was drawn with objective D, ocular 4. 
Fic. 7. Section taken in s, (of Fig. 2), showing that no nerves leave the cord in 
this space. .a., neutral arch of vertebra; 7, filum terminale; .7., pia mater; d.m., 
dura mater; a.z., adipose tissue. 
Fic. 8. Section taken in s, (Fig. 2), showing the absence of outgoing nerves. 
n.a., neural arch of vertebree; f, filum terminale; a.¢., adipose tissue. 
Fic. 9. Section through s, (Fig. 2), showing the presence of the last pair of out- 
going pair of spinal nerves. 2.a., neural arch; #., nerves cut obliquely; 7, filum 
terminale. 
Fic. 10. Cross-section of cord in place taken more anteriorly, — in 5s, or s,,— 
including a longitudinal section of the long ganglion, g., on the dorsal root of the 
nerve; #.q@., the neural arch of vertebrze; 7.7., pia mater; @.., dura mater; /, the 
lumen of the cord; g., the ganglion. The section, being taken a little obliquely, 
shows the two roots of the nerve upon the left side before their union. On the right 
side the ganglion cells are shown in the outgoing dorsal root. 
