70 
DR, G. E. BEEVOR AlsD MR. Y. HORSLEY OR THE EXCITABLE 
exciting current was an interrupted induced current obtained from the secondary coil 
of a Du Bois Eeymond inductoriiim, supplied by a 1 litre bicliromate cell. The 
distance of the secondary coil from the zero point of completely covering the primary 
was such as to give a minimal stimulus, and this was usually about 10 cm. 
After the experiment was completed the animal was killed by excess of chloro¬ 
form, the hemisphere removed, washed in salt solution and the surface photographed. 
Upon the jrhotograph thus obtained, the numbers representing the different bundles 
of fil)res (1 mm. square) were transferred by compasses from the plan originally drawn 
on the ruled paper. 
Mode of Enumeration and Recording Residts .—We have just said that we 
numbered the millimetre squares of the internal capsule in order from before back ; we 
adopted this plan for the reason that as the anterior limit of the excitable portion of 
the capside varies in position, i.e,, retreats as the section descends [cf. fig. 1.), it vras 
necessary to express the position of the fibres having the same function by some 
means which should bear an absolute value in relation to the rest of the capsule. By 
this means we have been enabled to trace the bundles having the same function 
through their various changes of direction as they pass down through the different 
sections of the capsule to reach the crus. 
Inasmuch as the capsule is divided into millimetre squares by the above method, 
each figure denoting any bundle of fibres represents at the same time the distance of 
that bundle from the front end of the anterior limb. 
In plotting out the j)lan of the capsule during an experiment we arranged it so that 
the more important posterior limb should be drawn parallel to one direction of the 
rows of squares on the ruled paper ; consequently, as the anterior limb forms an 
obtuse angle with the posterior limb, the squares dividing it were necessarily 
echelonned. This, however, afforded no real difficulty, and the more so since in the 
most important sections very little of the anterior limb is excitable. We, therefore, 
expressed each square or bundle of fibres by a fraction, the numerator of which 
denoted the distance that it was situated from the anterior end of the capsule, while 
the denominator gave the total length of the capsule in that particular section; in 
this wise one fraction, or, in otlier words, the position of one bundle of fibres in one 
section, is strictly comparable with that in another section. 
In order to bring all the fractions thus obtained together, and to find the average 
position of the representation of any given movement in each group, we converter! all 
the fractions into decimals to two places. We took two places as adequately accurate, 
since any error beyond would only amount to of the length of the capsule, and 
as this actually amounts, on the average, to not more than ‘02 mm., it is a length 
which is far too small to be considered among the errors of the experimental method. 
The decimals thus obtained, denoting the squares indicating the localisation of 
each movement elicited, were next added together in the several groups, and the 
average taken. 
