198 THOMPSON YATES LABORATORIES REPORT 
2. The nucleus has a clearly defined membrane, and consists of a clear portion in which is 
the red-stained chromatin network. The nucleolus is large and stained deeply blue. 
3. The body of the cell is stained red, and throughout is densely covered with the blue 
stained Nissl bodies. In thinner sections the contrast between the differently coloured parts of 
the cells is more marked. In an ordinary cell from the anterior horn of the spinal cord the 
stichochrome arrangement of the Nissl bodies gives to the cell a distinctly streaked appearance, 
which is spoken of by Von Lenhossek as ' tigroid.' Held ( loc. cit.) has studied especially the 
intimate nature and origin of the Nissl bodies, and has shown that anatomically they consist of the 
finest granules, and that between these lie vacuoles. To see this condition it is necessary to cut 
sections from i — 2 /x in thickness. Vacuolation of this character was rarely seen in any of my 
preparations in sections about 7 p. thick. 
4. The dendrons also stain red, and along their course are the Nissl bodies. 
In connection with the normal cell I may mention that pigment was never found in the 
cell of the Cat or Rabbit, but plentifully in Man and the Monkey. The histo-chemical tests of 
Macallum show that the pigment does not contain iron in either organic or inorganic combina- 
tion. 
I.— ON THE CONDITION OF THE SPINAL CORD OBSERVED AFTER 
SECTION OF SEVERAL POSTERIOR ROOTS 
Method of operation. — Laminectomy was performed under strict antiseptic precautions. 
Only sterilized warm normal saline was used for sponging purposes after the muscles had been cut 
through. The dura mater was freely opened and the roots cut in the region of the cauda equina 
about \ of an inch from their entrance into the spinal cord. 
In all cases quoted the wound healed without suppuration. The segmental number of the 
roots cut was ascertained in each case by post-mortem dissection, counting from the last ribs. 
The number of ribs was thirteen on both sides in all cases. 
Naked eye appearance of the cord. — There was an entire absence of meningitis. A small 
amount of soft tissue was often found loosely adhering to the dorsal aspect of the cord ; it was 
easily removed, and the underlying surface of the cord appeared in most cases quite normal, in 
some slightly discoloured. 
Examination of the cord. — A very large number, i — 3 hundreds of sections, were cut from 
each of the several spinal segments and stained in the manner described. On examination a large 
number of markedly altered cells were found showing the changes detailed below. 
Characteristics of the affected cells. — These present different appearances. 
I. The most striking and perhaps the commonest form is that shown in the figure. As 
seen under an apochromatic lens mm. 3.0, aperture 1.40, compensating Oc. I2, it presents the 
following features : the nucleus is markedly eccentric, it has a clearly defined membrane and 
well-marked chromatin network. 
The nucleolus is well defined. The chromatic masses have completely disappeared from 
the greater part of the cell, and are localized round the nucleus. It is noteworthy that the Nissl 
