2 E. M. NELSON ON STRIPED MUSCLE FIBEE OF PIG. 



fifteen years, the truth, of the perforated diatom structure, as 

 seen under a wide-angled cone, has been conclusively proved, in 

 spite of the most emphatic utterances about the impossibilities 

 of doing so ; what has been done with diatoms may be done 

 with histological tissues. 



In the first place, the minuteness of an ultimate fibril is 

 not sufficiently recognized. The following measures compare 

 favourably with those in my former paper, which were not 

 those of the same specimen, and which were not measured 

 photographically. 



The single fibril here is yj^oir ii^ch in diameter; its thick- 

 ness is probably ^^ „ l^^J^^ inch (estimated, not measured), and 

 the distance from one membrane of Krause to the next is barely 

 tttAtto i^icli. This small portion contains no less thau eight 

 stripes. Their order is as follows : — 



1st. The very dark and conspicuous membrane of Krause. 



2nd. A very bright stripe. 

 , 3rd. A faint dark stripe. 



4th. A light stripe, not nearly as bright as No. 2. 



5th. A dark stripe, darker than N^o. 3, but not as dark as 

 No. 1. 



6th. A light stripe, similar to No. 4. 



7th. A dark stripe, similar to No. 3. 



8th. A very bright stripe, similar to No. 2. 



After this we come again to the dark membrane of Krause. 

 Each band, therefore, may be said to be about )^ ,, I ^^ ^^ inch in 

 diameter — this, of course, supposing them to be all equal. 



In the early days of microscopy nothing but the coarse, 

 alternating white and dark bands were seen ; and it is to these 

 coarse bands that " striped muscular fibre " owes its name. 

 What is now called Krause's membrane, viz., the conspicuous 

 dark line traversing the white band, has been known for long. 

 It is figured in a plate dated 1852 ; there is no doubt it 

 could have been easily seen with objectives constructed after, 

 say, 1841. The next we have is an alleged bright stripe divid- 

 ing the large dark portion between the Krause membranes into 

 two equal parts. This, which is called Hensen's stripe, has been 

 frequently the subject of controversy, some saying that it is an 

 optical ghost. If you will look at the figure you will see no 

 white stripe, but in place of it a very narrow dark stripe, with 

 a white one on either side of it. You will notice that, in my 



