INTERCALATED DISCS OF HEART MUSCLE 



167 



22 



Fig. 22 Cardiac muscle of guinea-pig of first week of post-natal life. The 

 discs are abundant, but exclusively of the granular (or less compact) narrow disc 

 type. 



Fig. 23 Cardiac muscle of guinea-pig of last week of gestation. Cross stria- 

 tions and discs are just beginning to make their appearance. 



IV. DISCUSSION 



An attempt to establish a relationship between rate of heart- 

 beat and the number of discs was unsuccessful. If a series of 

 animals, ranged according to the reported and observed relative 

 abundance of intercalated discs, be compared with the same series 

 ranged according to the rate of heart-beat, a correspondence 

 appears at certain points between as many as three successive 



