1881.] 



MICKOSCOPICAL JOIIKNAL. 



211 



I had made on the large ganglion- 

 cells of the cord and their numerical 

 relations to the motor fibres. 



The fact that irritation of the frog's 

 spinal cord causes titanus is not new, 

 but no attempt had previously been 

 made to exactly determine the portion 

 of the cord concerned in this phe- 

 nomenon. 



The mode of experiment was as 

 follows : The brain of the frog was 

 destroyed and the animal fastened up- 

 on a small board,and secured in such a 

 way that its spinal column was firmly 

 fixed. The spinal cord was then ex- 

 posed throughout its length, especial 

 care being taken not to wound it or 

 to injure the roots of the nerves. 

 Bleeding was also prevented so far as 

 possible. The tendo Achillis was 

 then severed from its attachment and 

 connected by a band to the pen of a 

 revolving drum, on which the move- 

 ments of the gastrocnemius muscle 

 were thus recorded. 



The first experiments were devoted 

 to localizing the tetanus-centres longi- 

 tudinally in the cord and to investigat- 

 ing whether an irritation of one side 

 of the cord caused a tetanus of the 

 other side. Two modes of irritation 

 were successfully tried — puncture 

 with a sharp needle,and pressure with 

 a blunt one. The first was, of course, 

 much more local in its effect than the 

 second. By beginning to pinch the 

 cord, at, say the origin of the second 

 nerve, and passing backward, no ef- 

 fect was produced on the gastrocne- 

 mius muscle or the hind limbs until 

 just at the origin of the seventh nerve. 

 Then a slight tetanus was produced. 

 Beginning to irritate at the hinder 

 end of the cord and passing forward, 

 the posterior limit for this tetanus- 

 centre was found to lie just at the 

 hinder end of the origin of the ninth 

 nerve. Irritation of the region inclu- 

 ded between the origins of the seventh 

 to the ninth nerves, inclusive, called 

 out a tetanus in the hind leg of great- 

 er or less duration. The point of 

 maximum irritability lies near the 

 origin of the eighth nerve. 



It was further found (ist), that irri" 

 tation of the cord on one side pro- 

 duced no effect on muscles of the 

 other side ; and (2d), that the larger 

 the area of the tetanus-centre affect- 

 ed, the more vigorous and long-con- 

 tinued the tetanus. Thus pressure 

 with a blunt needle produced much 

 more effect than puncture with a 

 sharp one, and the effect of the latter 

 needle was smaller in proportion to 

 its smallness and sharpness. It was 

 further found that irritating the mo- 

 tor roots of the nerves in the same 

 way as the cord produced only a con- 

 traction, never a tetanus. 



At this stage of the experiments 

 electrical irritation was tried, but un- 

 successfully. The pressure of the 

 electrodes was sufficient to excite the 

 mechanical and electrical effects. 



More recent efforts at localizing 

 the centre were then made. First, 

 portions of the cord were cut away by 

 passing through the cord thin pieces 

 of platinum wire, hammered flat, 

 sharpened and polished. In this way 

 the posterior columns of the cord, the 

 sensory roots of the nerves, a great 

 portion of the lateral columns and 

 the posterior zone of the grey matter 

 were removed without affecting the 

 functions of the cord as a tetanus- 

 centre. Attempts at removing the in- 

 terior columns failed, because it was 

 found very difficult to remove these 

 without at the same time injuring the 

 anterior zone of the grey matter. The 

 method is at best rude and is liable 

 to cause injuries beyond the limits of 

 the portion removed. It, however, 

 showed that this function of the cord 

 was located in either the anterior col- 

 umn of the white matter or in the an- 

 terior zones of the grey matter. 



It is well known that in the last- 

 named part of the cord there lies, in 

 the frog, a peculiar group of large 

 ganglion-cells, closely united to each 

 other, and probably to the motor 

 fibres. It was natural to regard these 

 as the seat of this function, and new 

 experiments were resorted to in order 

 to locate the point more exactly. In 



