I50 THOMPSON YATES LABORATORIES REPORT 
rigidities after cerebral ablations in the Monkey, I should quite agree with him that in the 
constant assumption of the sitting pose in cramped cages, an important adjuvant condition in the 
production of late rigidity in the Monkey has been discovered by him. At the same time, in the 
occurrence of late rigidity of the lower limbs after spinal section, I look upon a natural inequality 
of reflex spinal play in, or employment of, individual spinal mechanisms {e.g.., reflex spinal flexion 
of knee, and reflex spinal extension of knee respectively), and the gradual, almost inevitably 
resulting loss of functional balance between antergic sets of spino-muscular apparatus as the prime 
factor. For instance, flexors of the knee become contracted when the cord is transected, because 
extensors, practically inaccessible to spinal reflexes of short path and of ordinary stimulus-intensity, 
never exert tliat normal maximal stretching which, even if artificially given from time to time, 
successfully defers tlieir surrender to contracture. My view is that the contracture is the 
expression and result of the over-balance of the spinal tonus of the extensors of hip and knee by 
that of the flexors. The normal tonus of the skeletal muscles when the nervous system is intact 
has, doubtless, spinal, cerebellar, and cerebral factors, which are in it algebraically summed. In 
the spinal experiments now under consideration of these several factors, only that of the cord 
itself is effective, the transection having cut off all the others, and in these contracture experi- 
ments necessarily only that of the lower half of the cord. That remnant of the normal tonus I 
refer to as spinal tonus, in contradistinction to the tonus described at p. 163 in this paper, ensuing 
on ablation of the cerebral hemispheres, which I term decerebrate tonus, also in contradistinction to 
that tonus which I term decerebellate ensuing on removal of the cerebellum. The late rigidity 
of paraplegia in the Monkey is an expression of the upset of balance of the spinal tonus in 
antagonistic muscle-groups. I look upon its origin as of reflex* nature, and this is borne out by 
the fact that in my Monkeys it could, in its earlier stages, i.e., before structural changes in the 
muscles set in, be set aside by chemical anaesthesia, and by applying an Esmarch bandage to the 
limbs. The unequal degree of spinal tonus, idem aliter of spinal reflex action is, in my view, of 
prime importance in the production of late rigidity. 
This view appears to me consonant with, although widely removed from, that advanced by 
H. MuNK. It harmonizes with his view in so far that confinement in a cramped cage might still 
further reduce the opportunity for extension of the knee or hip, even when that movement 
occasionally arose. It may be objected tliat if, as I urge, there is a considerable and constant 
difference in spinal excitability between the motor spinal centres for flexors and extensors, e.g., at 
hip and knee, such should be demonstrable ; but, as I have shown,t strychnia spasms involve 
extensors and flexors, e.g., at knee and ankle, synchronously and impartially, although according to 
doctrine! of reflex spinal origin. It is, of course, well known since Sanders-Ezn§ (1867) that 
the very spinal nerves whose motor roots by direct excitation produce extension of knee, when 
reflexly excited evoke flexion of knee ; on the other hand, I am not convinced that in the 
Mammalian cord strychnia spasms are always of purely reflex nature. The spasms of asphyxia are 
often certainly not reflex, but direct ; and in spite of the excellent experiments of H. E. Hering 
* 'Pioc. Roy. Soc.,' vol. 53, 1893. :J: Compare lately Ewalil Hering, Pfliiger's ' Archiv,' 1893. 
t ' Jourii. of Physiol.,' vol. 13, 1S92. § Liulwig's ' Arbeiten, " Sitzungsb. (1. Siichs. Ges. d, Wiss." ' 
