1907.] Innervation of Antagonistic Muscles. 343 



In the scratch reflex, the reflex, though from each point of skin in the 

 receptive field a scratch reflex is produced, varies in certain characters as the 

 locus of stimulation in the receptive field is shifted. The scratch reflex, 

 considered as a generic type (the type reflex)* is, therefore, not really one 

 reflex but a group of allied reflexesf differing somewhat one from another, yet 

 presenting certain similar characters in common. The same is true of the 

 flexion reflex of the limb. Although the movement is always flexion of the 

 limb, the flexion tends to differ somewhat according as this or that skin- 

 point, or this or that afferent nerve branch, is the seat of stimulation. 

 These differences are more easily apparent in my experience under weak 

 stimulation than under strong. The flexion reflex as a generic whole (the 

 type reflex) is, therefore, not strictly one reflex, but is a group of allied 

 reflexes, closely similar in general character, yet possessing individual 

 differences one from another. 



V. The crossed reflex excited in a hind limb by stimulation applied to 

 the fellow limb of the opposite side exhibits, in my experience, a regularity 

 almost as marked as does the uncrossed flexion reflex. The distribution of the 

 effect seems mainly, if not entirely, to muscles affected by the uncrossed 

 reflex. The crossed reflex has been elicited in my experiments by stimulation 

 of the following afferent nerves: The plantar nerves, the anterior tibial 

 close above the ankle, cutaneous branch of the musculo-cutaneous division 

 of the peroneal, external saphenous, external cutaneous, internal saphenous 

 at various heights up the limb, the nerves of tibialis anticus, extensor longus 

 digitorum, peroneus longus, p. brevis, p. quartidigiti, vasto-crureus, gracilis, 

 pectineus, adductor, and the larger nerve-trunks, such as obturator, peroneal, 

 popliteal, and hamstring nerve. In the case of these nerves, the reflex 

 effect observed in the crossed hind limb has been contraction of crureus, 

 vastus lateralis, vastus medialis, adduciores, semi-membranosus, gastrocnemius, 

 and soleus. The resulting movement has been observed to be extension at 

 knee, ankle, and hip. This movement is observed not only in the cat and 

 dog but in the rabbit ; though in the rabbit, in the ordinary progression of 

 that animal, the hind limbs flex and extend synchronously usually instead of 

 alternately as in cat and dog. 



When psoas, gracilis, semi-tendinosus, biceps cruris (posterior part), tensor 

 fascice femoris, and extensor longus digitorum are examined in the crossed 

 reflex, they are, in my experience, not seen to contract. One might imagine 

 that the reflex exerted no influence on them. But of this one cannot be 



* ' Integrative Action of the Nervous System/ p. 127 ; ' Ergebnisse d. Physiologie,' loc. 

 cit., p. 822. 



t ' Brit. Assoc. Eeports,' 1904. Address to Sect. I. 



