244 MR. MORLEY ROBERTS ON TUE FUNCTION OF 



aspect, powerfully suggested an organized or cured aneurism. 

 Many must have made the same observation, even if they have 

 not come to similar conclusions. The anatomist and pathologist 

 perhaps know their subjects too well and are necessarily greatly 

 dominated by current theory. The general adaptation of the 

 heart to the work it performs may well delight the anatomist as 

 he studies its machinery. His main business is not evolution. 

 The pathologist on the other hand, observing its many failures, 

 is scarcely likely to discern that by failure itself may come 

 eventual perfection, and while the physiologist considers its 

 functions rather than its apparatus, he studies it as it is, not as 

 it was. In each case the observer may not see the forest for the 

 trees. Yet when we look at the partially repaired aneurism with 

 its fibrous growths and turn to the opened heart, the essential 

 relationship of the chordca tendinece, for all their definite functions, 

 to the rude fibres of an aneurism is obvious. Is such a likeness 

 an accident of evolution and pathology, or are we to consider the 

 heart as much an organized dilatation sac of the whole fused 

 circulatory canal as the cured aneuiism is of a. part of it ? It is 

 in embryology that we seek for confirmation of what is suggested 

 by anatomy. But even anatomy alone offers powerful proof of 

 the view that the heart, as we know it, is the latest result of 

 i-epeated failures of the circulatory canal under strain and of the 

 repairs effected by the stressed tissues in their response to 

 changed and abnormal stimuli, just as bone alters under its 

 particular stresses. During .embryological life there is found in 

 the heart a small patch of non-functioning muscle in the anterior 

 segment of the mitral valve. Its presence is intelligible if we 

 consider it a relic of a disrupted and repaired organ. The 

 muscles of the heart are obviously homologous with those of 

 the arteries. Yet they have become striated although they are, 

 of course, still involuntary. IS on-striated muscle is the earliest 

 in evokition. It seems that the increased functioning of the 

 cardiac muscle has converted it into its striated form so that it 

 resembles skeletal muscles, which are much more active than 

 non-striated muscle. The whole histology of cardiac muscle 

 probably represents the result of great stiains. Structures such 

 as the disks or bands of Ebarth are found no whei^e else and may 

 be the result of peculiar stress. There are even portions of 

 muscle which no longer perform muscular functions. Their 

 fibres do not contract but serve instead to conduct stimuli as 

 if they were nervous tissue. All tissue is conductive, but the 

 bundle of His, with its Purkinje fibres, which carries the impulse 

 from the sino-auricular or Keith-Flack node to the venti-icle, 

 transmits messages at ten or twelve times the normal muscular 

 rate. When it fails there is heart block. In the embryo the 

 valves arise from the cardiac walls and are composed of muscular 

 tissue which by the action of fibroblasts gradually become non- 

 muscular. This must have been originally a pathological process. 

 It is a reversion, a degeneration made use of. We observe 



