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The lungs of the Cetacea with special reference to the harbor porpoise (Phocaena phocoena Linnaeus).

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T H E LUNGS O F T H E CETACEA, WITH SPECIAL REFERENCE TO T H E HARBOR PORPOISE (PHOCAENA
PHOCOENA, LINNAEUS)
GEORGE B. WISLOCKI
Department of A n a t o m y , Harvard Medical Sclzool, Boston, Massaohusetts
TWO TEXT FIGURES AND ONE PLATE (TWO FIGURES)
I n two recent papers (Wislocki and BQlanger, ’40 ; B&langer,
’40) comparisons were instituted between the lungs of several
species of larger whales and those of certain dolphins and
porpoises. It was pointed out that the lungs of Cetacea have
certain features which characterize them all. Yet the lungs of
the large whales differ in one important respect from those of
the small Cetacea. It was demonstrated that the lungs of the
large whales (Balaenoptera sibbaldii, Balaenoptera physalus,
Physeter megalocephalus) possess excessively heavy myoelastic bundles in the septa1 borders of the air sacs and alveolar ducts, whereas no special system of myoelastic valves is
present in the smaller bronchioles. In the smaller Cetacea
(Delphinus delphis, Tursiops truncatus, Delphinapterus
leucas), on the contrary, the smallest bronchioles hare become
differentiated into a highly specialized “valvular segment”
(Edanger, ’40). This striking difference could have become
the basis for a generalization, separating the whales from the
dolphins and porpoises, were it not for the fact that Lacoste
and Baudrimont ( ’33) have denied the presence of myoelastic
sphincters in the terminal bronchiolar passages of the harbor
porpoise (Phocaena communis). Because of this discrepancy
the conclusion could not be drawn that uniformity exists
among the dolphins and porpoises in regard to the presence
of the “valvular segment.’’
117
118
GEORGE B. WISLOCKI
MATERIAL AKD METHODS
I n consequence of this, the opportunity was welcomed recently to re-examine the lung tissue of a harbor porpoise. The
material was placed at our disposal through the courtesy of
Mr. Harry C. Raven of the American Museum of Natural History, who obtained the specimen (A. 111. N. H. 2182 C. A) a t
Cape Breton Island and identified it a s a harbor porpoise
(Phocaena phocoena, Linnaeus). The lung tissue was examined by dissection under a binocular dissecting microscope,
and sections were prepared, stained with liematoxylin and
eosin, by the Azan technique, Masson’s trichrome mixture,
and by Weigert’s resorcin fuclisin for elastic tissue. A drawing is submitted of tlic smallest bronchiolar segment of
Phocaena, together with one, at identical magnification, of a
specimen of the lungs of Delphinus delphis which possesses
highly typical “valvular se,gments.” The lungs of this common ocean dolphin (Delphinus delphis) were obtained through
the courtesy of Mr. Arthur F. &Bride of Marine Studios,
Florida. The lung tissue of the latter was prepared for study
in the same way as that of the harbor porpoise.
OBSERVATIONS
Figure 1illustrates the morphology of the smallest broncliiolar passages of the harbor porpoise and should be compared
with the drawing, a t identical magnification, of the same segment of the dolphin’s lung. It will be observed that the smallest broncliioles of the harbor porpoise do possess sphincter
valves, although they are distinctly less numerous and more
delicate tlian those of Delphinus (fig. 2), or Tursiops and
Delphinapterus (Wislocki and Bdanger, ’40 ; Bdanger, ’40).
In the harbor porpoise there does not appear to be a succession
of more than eight to twelve valves in a single terminal bronchiolar passage, whereas in the larger porpoises and dolphins
as many as several dozen are present in a valvular segment.
Because of this relative restriction of the extent of the valvular
se,gments in the harbor porpoise, valves are not encountered
as frequently in ordinary histological sections as they are in
LUNGS O F HAKBOK PORPOISE
119
lung sections of the somewhat larger related species. Yet in
sections, especially when stained by the Azan method, Alasson’s trichrome mixture, or with Weigert ’s resorcin fuchsin,
instead of with hematoxylin and eosin, typical myoelastic
Fig. 1 A drawing of a valvular segment of the bronchiolar trec of a harbor
porpoise, showing the characteristic myoelnstic sphincters subdividing the broncliiole into compartments. X 14.
Fig. 2 A drawing of a valvular segment of the bronchiolar tree of a dolphin,
a t the same magnification as the preceding figure, t o illustrate the identity of the
valvular segment in these two species. Observe that the mpoelastic sphincters are
inore nnnierous and larger than m the harbor porpoise. X 14.
120
GEORGE B. WISLOCRI
valrcs can be recognized with 110 gi‘eat difficulty (figs. 3 and 4).
Thus, contrary t o tlie statement of Lacoste arid Baudrimont,
tlie lungs of the harbor porpoise possess typical valvular segmcwts similar to those of other porpoises arid dolphins which
liave been examined.
111 other respects, also, the structure of the lungs of the harbor porpoise is identical with that of Delphinus, Tursiops arid
Delphinapterus. As in the latter, the lungs a r e characterized
by the l,i-esence of cartilaginous armature extending dowii to
tlie respiratory sacs, by the occurrence of a double capillary
net in the interalveolar septa, and by a relatively large amount
of collagenous and elastic tissue f orming the supporting
framework of the bronchi, blood vessels and air sacs. Thus
we i.eucli the coiiclusioii that the essential lung structure of the
liarloor porpoise is identical with that of other porpojses and
dolphins which have been inrestigated.
W e are now iii a position for the first time t o propose the
generalization that the lungs of the porpoises and dolpliins
cliffel. materially from those of wliales hy the evolution in the
smallcist hroncliiolar passages of a specializcd valvular segment containing mpoelastic sphincters. The characteristic
featu i’es and homologies of ihe valvular segmerii have been
described and discussed at sufficient length in provious papers
(TTislocki and IEi.lanqcr, ’40 ; K6langer, ’40) to make it unnecessar!. t o recapitulatci thcm here.
SUMMA BY
The essential lung histology of the harbor porpoise (Z’hocaena pliocoena) is identical with that of other porpoises and
tlolpliiiis which have been investigated. Like tlie latter, the
linigh of the harbor porpoise are characterized h p the possession of a specialized system of myoclastic sphincters constituting a “ ~ a l v a l a rsegment,” involving the srriallest bronchiolar passages. The conclusion is reached that a specialized
ralvulnr segment is characteristic of the lungs of porpoises
and dolphins, iii contrast to wliales, the lurlgs of mhicli do not
ex1iil)it this specialized structure.
LUNGS O F HARBOR PORPOISE
121
LITERATURE CITED
B ~ A N G ELEONARD
R,
F. 1940 A study of the histological structure of the respiratory portion of the lungs of aquatic mammals. Am. J. Aiiat., vol. 67,
pp. 437461.
LACOSTE,
A., A N D A. RAUDRIMONT1933 Dispositifs d ’adaptation fonctioiiiielle
B la plong6e dans l’appareil respiratoire du Marsouin (Phocoena communis, Less.) Arch. d’anat., d’histol., et d’embryol., vol. 17, pp. 1-48.
WISLOCKI,G. B., AND L. F. BBLANGER1940 The lungs of tlie larger Cetacea
compared t o those of smaller species. Biol. Bull., vol. 78, pp. 289-297.
PLATE 1
EXPLANATION O F F I G U R E S
3 Section of a lung of a harbor porpoisc stained f o r elastic tissue (Weigert’s
resorcin fuchsin), showing several iiiyoelastic sphincters constricting a bronchiole.
X 70.
4 Section of a lung of a harbor porpoise stained by Massoii’s triclironie mixture, showing a characteristic myoclastic valve. x 150.
122
PLATE 1
LUNGS O F HARBOR P O R P O I S E
GEOBRB B. WISLOCXI
123
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