116 Prof. C. S. Sherrington and Dr. E. E. Laslett. [Nov. 5, 



like a cleaned slate, on which once more a new degeneration can be 

 written without fear of confusion with a previous one. The cord is 

 then ready for receiving the lesion which shall cause degeneration of 

 the particular tracts whose existence is suspected. After a period 

 suitable for the full development of the new degeneration, the cord is 

 treated histologically by the Marchi method, and the microscopical 

 examination proceeded to. This method resembles in principle a 

 method employed with noteworthy results by Miinzer.* This author 

 performed on the new-born rabbit a first lesion (e.g., removal of one 

 cerebral hemisphere, injury of mid-brain or cord), and later, in the 

 animal when groAvn, proceeded to establish a new lesion which was 

 thus uncomplicated by the part already separated: thus "Gudden's 

 agenesic atrophy " was made to precede the degeneration desired for 

 study. 



One of the experiments made by Miinzer and Wiener (1895) deals 

 with the problem undertaken by ourselves. After semi-section of the 

 spinal cord of the new-born rabbit at the last dorsal segment, they per- 

 formed total transection two segments further back when the animal 

 was grown. Behind the second section they found " as many fibres 

 degenerate on the semi-sected side as on the intact side." If not " decus- 

 sation fibres " these fibres must evidently be of intra-spinal origin in the 

 anterior lumbar region. As to their being decussation-fibres, Miinzer 

 says they are, on the contrary, from the grey matter of the same side 

 as the semi-section, a statement which our own results in the dog in 

 the same and other regions endorse. 



In our experiments the cord of the dog has been used, and total 

 transection has not been the final, but the first step in the pro- 

 cedure. This course was chosen in order to completely exclude all 

 chance that fibres from sources not the object of inquiry could compli- 

 cate the second lesion. In order to ensure complete transection, we 

 have in almost all our experiments exsected and ablated a short 

 segment of the cord, instead of simply severing it across. The 

 exsection was made immediately in front of those spinal segments 

 whose system of descending fibres in the cord was to be looked for. 

 Then after an interval, which we found by experience must not fall 

 short of 260 days, the second lesion, usually some form of partial 

 section, was performed, and a further period of about 20 days was 

 allowed for degeneration. The procedure of total transection prior to 

 the lower limiting lesion has an additional advantage in the lesser 

 interference with the local circulation of the cord in the final lesion. 

 Better in these respects this plan offers, however, considerably greater 

 difficulties than its converse. We have, in spite of all care, lost a 

 number of experiments in the long intervals necessary to elapse while 



* E. Miinzer, with. Wiener, ' Prager Medicin. Wochenschrift,' 1895; also 

 ' Monatschr. f. Psychiat. u. Neurol.,' vol. 12, p. 241, 1902. 



