14 TEANSACTIONS LIVEEPOOL BIOLOGICAL SOCIETY. 



is easy to understand that sixty muscle-fibres scattered in 

 a muscle consisting of many thousands may cause no per- 

 ceptible tightening of the tendon ; they may simply stretch 

 or compress adjoining inactive and elastic fibres. The 

 degeneration of these few fibres I look upon as strong 

 evidence of the morphological character of the overlap ; 

 the paucity of the fibres is one of the many facts which 

 indicate that the distribution of the motor-roots is arranged 

 on a segmental plan in accordance with the terms of a 

 bequest dating back to a time when the present environ- 

 ment of the limb, especially in its Mammalian form, had 

 no preponderant weight in the shaping thereof. As re- 

 gards functional value this character of the Mammalian 

 limb is on a par with details of structure which are not 

 specific, and, therefore, with other details of structure 

 outside these immediately acquired by the species, not to 

 be considered as of necessity of functional importance. 

 The functional use of the contribution of one or two nerve- 

 fibres to a muscle requiring hundreds is difficult to see ; 

 the probability of the occurrence of such poverty-stricken 

 contributions is, on the view of the morphological neces- 

 sity of the ray-arrangement of the limb musculature, so 

 high as to be only what might have been expected from 

 theoretical considerations. The fact that certain of the 

 motor-roots of the limb contribute fibres to the innerva- 

 tion of certain muscles in such scanty number as to be 

 ineffective for movement is a further argument for the 

 morphological rather than functional character of the 

 motor-root distribution in the Mammalian limb. A number 

 of motor-fibres, too small to evoke appreciable movement 

 in a muscle when excited electrically, will hardly be effective 

 for movement under the action of the will. 



Strongly militant against the functional theory of the 

 motor-root is the frequent occurrence and wide range 



