598 THE DISEASES AND DISORDERS OP THE OX. 



cilia and flagella and the primitive muscles of infusoria to the 

 highest forms, showing that fully-developed muscle is actually 

 poorer than elementary protoplasm, in the point that muscle 

 is wanting in automatism and elementary nervous properties. 

 The muscle-cell is not complete without the nerve-cell connected 

 with it by the continuous nerve-fibre, which may be several feet 

 long. Hence we have two separate cells united only for one 

 purpose, one being the nerve which excites, and the other the 

 muscle which obeys. It has been proved that nerve-branches 

 are not always present. Professor Kiihne has shown that small 

 pieces of fresh frog's muscle in which no nerve can be detected 

 by osmium-gold staining, whereby the finest nerve-fibres, if 

 present, can be displayed, neverthless twitched at each stimulus- 

 not below a certain stimulus, and he has also proved the fallacy 

 of the statement that everything which excites the nerve makes 

 the muscle twitch, and vice versa. Furthermore, the same dis- 

 tinguished scientist has shown that motor nerves can conduct 

 centripetally, i.e. in a direction opposite to that in which im- 

 pulses generally travel along them ; also that the absence of 

 nerves from a portion of muscle can be absolutely proved by a 

 physiological test, and that it is not possible to excite the 

 motor nerve of a muscle-fibre by any stimulus to the nerve-end& 

 within the muscle-fibre. Moreover, the excitement or contrac- 

 tion of a muscle does not travel back into its nerves. The great 

 majority of muscle-fibres are entirely free from nerves, the nerve- 

 endings being confined to very small tracts termed fields of 

 innervation. Hence muscle-fibres possess the power of propa- 

 gating their own excitation, the velocity of conduction being 

 from one-third to one-tenth of what it is for nerves. Thus the 

 nerve only introduces a stimulus to the muscle, which propa- 

 gates it by its own independent irritability in every movement 

 and throughout life. All the different kinds of stimuli, except 

 those which are gaseous, which are capable of acting on muscle 

 are capable of being resolved into the setting up of electricall 

 currents. Hence all irritability can be reduced to reactions to- 

 electrical processes, and hence vital electricity is of immeasurable 

 importance. Nerve-endings in muscles show the booked forms 

 of their branches turned as a rule towards each other, and also 

 the direct contact of the nerve-end with either the transversely 

 striped contents of the fibres or with the protoplasmic sarcoglia 



