THE HEART 47 



to have proved that cells which Lowit termed nervous, were really 

 not nervous but endothelial. Another investigator, Schwartz, con- 

 cludes that the so-called ganglion cells seen in the endocardium 

 and epicardium of the ventricle are really akin to if not actually 

 mast-cells. Recently also Bethe claims to have demonstrated by 

 his methylene-blue method that ganglion cells exist at the apex 

 of the ventricle. He admits that they differ slightly from what is 

 regarded as the normal type of cell, but he believes that they are 

 true ganglion cells. As a critic says, many people would call this 

 ganglion cell a connective tissue cell. 



The question of the distribution of both ganglion cells and 

 nerve fibres is therefore in a somewhat chaotic state. More work 

 is required it is of the greatest importance to know whether 

 every muscle fibre has a nerve network surrounding it, and also 

 whether ganglion cells exist throughout the heart. Lastly, it may 

 be asked Do nerve fibres exist in the A-V bundle ? The question 

 must be answered in the affirmative. It is said to contain nerve 

 fibres and a few ganglion cells. Fredericq does not believe that 

 nerve fibres actually pass through the bundle, and brings as 

 proof evidence which we quote later on. He also states that he 

 has histological proof of this, but I have not been able to find 

 this piece of work. 



D. THE HEART AS A MUSCLE 



The chief properties of the heart should be studied on that 

 part of the heart which contains no nerves. From what has been 

 written in the previous section it will be obvious that this is a 

 matter of no little difficulty. In determining these properties, 

 however, most experiments have been made upon the apical part 

 of the ventricle, on the assumption that this contains no nervous 

 tissue. Although we shall have occasion to refer from time to 

 time to the property of automaticity possessed by the heart, we 

 shall not in this section discuss in which tissue, muscular or nervous, 

 that property resides, but shall leave it until later, when we shall 

 consider this question together with the mode of conduction of 

 the excitatory wave which arises as the result of this property 

 of automaticity. 



The properties of cardiac muscle may be studied either when 

 the heart is at rest or when it is beating. We shall consider the 



