Joseph Marshall Flint 3 
recently Mall* who has contributed extensively to the subject stated 
that a definite, homogeneous membrane surrounds some of the tubules 
of the kidney, which reacts, in many respects, not like reticulum or white 
fibrous tissue, but quite like yellow elastic tissue. These lie within the 
fibrillated basket-work he had previously found by ,digesting frozen 
sections of the kidney. This means that we must reclassify these struc- 
tures and consider the entire group of basement membranes as consist- 
ing of two types, namely, the homogeneous and reticulated. For, while 
it is by no means certain that all the cell complexes of secreting glands 
are surrounded by homogeneous membranes, it is probable from the 
results of digestion experiments, that most secreting alveoli, acini, ducts 
and cell groups are embraced and supported by a membrane made up of 
a delicate interlacing meshwork of reticulum. We may find that many, 
if not most, of the glandular structures are embraced by homogeneous 
as well as the reticulated membranes, but the exact distribution of the 
homogeneous membranes can only be determined by a series of special 
investigations. Some method must be devised for the study of the 
origin of the homogeneous membranes, but the development of the 
reticulated fibrillar basket-work which embraces most glandular struc- 
tures is readily followed in a series of embryos by Mallory’s aniline blue 
fuchsin connective tissue stain,’ either used according to the original 
directions of Mallory or by the medifications more recently suggested 
by Dr. Sabin and quoted by Mall. 
It may be well to call attention to the fact, however, that the stain 
has to be modified somewhat for each set of preparations. Owing, per- 
haps, to chemical differences in the cells or exoplasm at different ages, 
varying pictures are obtained, even when the stain is allowed to act 
under precisely the same conditions. Moreover, it is also true that the 
blue is very easily washed out of many of the finer fibrils, often giving 
rather unequal pictures unless the duration of the action of the stain 
is rigidly controlled. 
In the preparations from which the following description of the de- 
velopment of the reticulated membranes is taken, the question. of the 
origin and relations of the demilunes of Giannuzzi is clearly settled, 
but these facts will be discussed later in another place. 
In a pig’s embryo, then, 3 em. in length, the submaxillary gland con- 
sists of a single tube with simple terminal arborizations lying below 
and medial to the ossifying mandible. At this time the gland is clearly 
defined from the adjacent structures because the dendritic branching 
2Mall. Bulletin of the Johns Hopkins Hospital, Vol. XII, 1901. 
3Mallory. Journal of Experimental Medicine, Vol. V. 
