JUNE 28, 1901.] 
In each of the subdivisions the subject is 
taken up systematically and in detail. For 
example: the lymphoid tissue in the oral cay- 
ity is discussed (1) as to its significance, (2) the 
migration of the leucocytes through the epithe- 
lium, (3) the structure of the lymphatic nodules, 
(4) the tonsils (lingual, palatine and pharyn- 
geal), and finally (5) the development of the 
tonsils. In summarizing the subdivision deal- 
ing with the tongue, Oppel arrives at the con- 
clusion that the mammalian tongue is to be 
derived from the entire tongue of the lower 
vertebrates and not merely from the back por- 
tion of it (as Gegenbaur believed). 
Especially in the case of the oral (salivary) 
glands has there been felt the need of a sum- 
marization of knowledge, and Oppel has fur- 
nished it admirably. The classification of the 
mammalian oral glands, their occurrence and 
structure in the different animals, have been 
made the subject of varied interpretations— 
Lavdowsky’s,. Klein’s, Nadler’s, Stohr’s and 
Ranvier’s are given. 
The interpretation of the demilunes of Gian- 
nuzzi of the mucous glands receives full discus- 
sion. The three views of the substitution theory, 
phase theory and special function theory are 
each presented and criticised. Oppel rejects 
the first two and considers the third as the one 
to be accepted in the light of recent work 
(Krause, Solger, Miller, e¢ al.). 
The pancreas seems to be of universal occur- 
rence in the vertebrates; wherever it has been 
sought for it has been found. Comparison with 
the salivary glands to see whether it can be re_ 
garded as an ‘abdominal salivary gland’ (the 
German name) shows that there are certain spe- 
cific structural differences that distinguish it. 
The pancreas is discussed from the point of 
view of the finer structure of the gland cells, 
including a consideration of the so-called para- 
nucleus, the activity of the cells, the form of 
the tubules, centro-acinar cells, the terminal 
ducts and the structure of the pancreatic ducts 
in the classes of vertebrates, the connective 
tissue of the gland. The interesting areas of 
Langerhans are next discussed, and in regard 
to their occurrence and significance, Oppel 
says that they have been demonstrated in most 
vertebrates (doubtfully in the Selachia). He 
SCIENCE. 
1025 
regards them as permanent structures and not 
transitory (as developing acini) and considers 
them of epithelial (entodermal) origin. On the 
other hand, whether or not they elaborate an 
internal secretion, he dares not decide, but 
should this be found to be the case, it does not, 
he thinks, militaté against the view that they 
were originally part of the gland proper giving 
(possibly) a clue to the structure of the primi- 
tive gland. Blood vessels and nerves are con- 
sidered next. The question of the occurrence 
of an accessory pancreas is then discussed. 
The development of the pancreas in the various 
vertebrate forms closes the chapter and is sup- 
lemented by a helpful table showing and com- 
paring the mode of development in the differ- 
ent vertebrates as ascertained by the different 
workers. 
In dealing with the various structures no 
attempt is made to discuss the gross anatomy 
as beyond the scope of the work, save in so far 
as necessary, though often—as in-wue case of 
the liver—references are given to the sources 
whence such information may be gained. It is 
likewise in accordance with the plan of the 
work to present the discussion in historical se- 
quence, so that the liver is considered from the 
standpoint of (a) the liver lobule, and (0) 
the liver cell and gall capillaries, despite 
the fact that liver lobules are peculiar to mam- 
mals. 
In the consideration of the remaining struc- 
tural features of the liver, bile-duct and gall 
bladder are taken up, followed by a discussion 
of the liver in the different vertebrates. The 
development of the organ constitutes the clos- 
ing division. Few original observations or 
generalizations are made in this portion of the 
work. 
The comparison of the liver with other typi- 
eal glands receives considerable attention, to- 
gether with the question of the anastomosis of 
the gall-capillaries, and the conclusion is reached 
_ that a net-like arrangement of the gall capil- 
laries occurs in the lower vertebrates, and in the 
higher forms at least in early development. 
Under the subdivision dealing with the func- 
tional activity of liver cells, the glycogen, pig- 
ment and fat content are discussed. Most in- 
vestigators agree that there are two kinds of 
