12 H. HAYS BULLARD 



granules of irregular form so frequently present in human muscle, 

 especially in cardiac muscle. 



Fat droplets occur in varying sizes. Apparently the smallest 

 droplets are beyond the limit of microscopic vision. Bell ('11), 

 staining muscle fibers b}^ Herxheimer's method, shows 'liposomes' 

 (his fig. 4, plate 16) which measure less than 0.5 mm. after a magni- 

 fication of 1300. This means that they have a diameter of less 

 than 0.5 n. According to Heidenhain ('00), 0.2 ju is the extreme 

 lower limit of microscopical vision (n. a. 1. 4), and if perchance 

 any structure of smaller size were visible it would still appear 

 to have a diameter of 0.2 micron. Herxheimer's Scharlach R, 

 as well as Nile blue frequently forms precipitates in the tissues 

 but precipitate granules lack the refractive character of fat drop- 

 lets and when of appreciable size the two are easily distinguishable. 

 Precipitate in a finely granular form may be confused with minute 

 fat droplets, and for this reason I have preferred to regard as 

 probably a precipitate, all granules having an approximate diame- 

 ter of 0.5 n or less. The diameter of the fat droplets, which di^ ers 

 with the nutritive condition and with the species of the animal, 

 seldom, if ever, exceeds 3 m in normal mammalian muscle. Fresh 

 preparations stained in Herxheimer's Scharlach R often show drop- 

 lets as large as 5 to 6 ju> but the examination of fresh material to 

 which no foreign fluids have had access has convinced me that such 

 large globules arise by the confluence of smaller droplets. 



The fat droplets seldom show a regular arrangement within 

 muscle fibers in preparations made from fresh material without 

 fixation. To demonstrate the position of fat droplets, portions 

 of muscle were stretched upon card board or small pieces of glass 

 and while still warm placed in 20 per cent formalin in a 0.75 per 

 cent solution of sodium chloride. After fixation of two to twenty- 

 four hours, sections were cut on the freezing microtome and stain- 

 ed by Herxheimer's method or by the Nile blue method. 



Figure 3 shows the droplets in a portion of a longitudinal section 

 of a dark muscle fiber from the pectoralis major of an adult cat. 

 The droplets are in transverse rows in segment J on either side 

 of the membrane of Krause, Z. An arrangement in longitudinal 

 rows is also apparent. Figure 4 represents a portion of a light 



