The Heart of Some Lungless 
Salamanders. 
G. S. HOPKINS, D.Sc. 
CORNELL UNIVERSITY, ITHACA, N. Y. 
Reprinted from the American Naturalist, October i, 1896 1896.] 
Zoology. 
829 
ZOOLOGY. 
The Heart of Some Lungless Salamanders.1-The recent 
literature of zoology has, perhaps, contained nothing more unexpected 
and startling than that certain adult salamanders are entirely lacking 
in those respiratory organs which, heretofore, have been deemed in- 
dispensable to the existence of animals so high in the zoological scale 
as the Amphibia. This total lack of lungs and branchiae appears the 
more marvelous when we remember that they are absent in forms which 
lead a rather active and wholly terrestrial life, as well as in those of 
more or less purely aquatic habits. 
Two questions are naturally suggested by this apparently aberrant 
condition of the respiratory organs. First, what structures or organs 
have taken on the functions of the lungs and branchise? and secondly, 
is there any modification in the form or structure of the heart which in 
any way may be correlated with the above mentioned peculiarities of 
these lungless forms ? 
The first of these two questions has been discussed to some extent by 
Prof. Harris H. Wilder, of Smith College, who first published an ac- 
count of this apparently anomalous condition. He concluded that res- 
piration was probably carried on by the skin and, perhaps, to some 
extent, by the mucosa of the intestine. Prof. Camerano has also pub- 
lished the results of some experiments upon two European forms which 
bear upon this same question. He believes that in these lungless forms 
respiration is effected in the bucco-pharyngeal cavity, and that the skin 
affords no efficient aid in the respiratory processes. 
In a still later paper he discusses the subject further, and tries to 
account for the disappearance of the lungs. Of one aquatic species (of 
the genus Molge) he says: " The function of the lungs as hydrostatic 
organs, is very marked." " In the clearly terrestrial forms one would 
say that the diminution in importance of the function of the lungs as 
hydrostatic organs induces a retrogressive development of them while 
1 Head before the Amer. Assoc. Adv. Science, Aug. 24, 1896. 
58 The American Naturalist. 
830 
[October, 
at the same time the importance of the bucco-pharyngeal respiration is 
increased." 
It appears to the writer that Camerano's conclusions need to be 
tested by further experiments, especially the part referring to the res- 
piration, for the area of the dermal surface far exceeds that of the 
bucco-pharyngeal cavity, and the skin is also very richly supplied with 
blood vessels which are so close to the surface that it would appear 
as if the gases of the blood and air might be readily interchanged. 
It is hoped that time will permit of some experiments on this point 
during the coming year. 
As to the second question, whether there is any appreciable modifi- 
cation of the heart in these hingless salamanders, nothing whatever has 
been published. 
It is the object of this paper to call attention to the fact that there is 
a difference in the heart of those salamanders that do not have lungs 
and those which do have them. So far as I have examined, it is possible 
to distinguish between the two forms by examining the heart alone. 
In order that what is said on this point may be clearly under- 
stood by every one, and in order to bring out the differences between 
the two more sharply, if possible, I wish first to recall to mind the 
structure of the Amphibian heart and then contrast with it the rela- 
tions as found in the heart of a lungless individual. We may take 
Huxley's description of the Amphibian heart as our standard of com- 
parison. In his Anatomy of Vertebrates he says: " The heart presents 
two auricles, a single ventricle and a bulbus arteriosus. A venous 
sinus, the walls of which are rhythmically contractile, receives the 
venous blood from the body and opens into the right auricle. The left 
auricle is much smaller than the right and a single pulmonary vein 
opens into it." In regard to the septum of the auricles, he says that 
" it is less complete in Proteus, Siren and Menobranchus (Necturus) 
than in other Amphibia. In Menobranchus the septum is reduced to 
little more than a wide meshed network of branched muscular bands, 
and in Proteus the existence of a septum is doubtful." 
The heart of our common Newt (Diemyctylus viridescens) Fig. 1 or 
of the large yellow-spotted salamander (Amblystoma punctatum), for 
examples, corresponds perfectly with Huxley's description. In both of 
these forms the auricular septum is perfectly complete, the cavities of 
the auricles being entirely separated, except just at the auriculo-ven- 
tricular aperature, at which point the two auricles communicate with 
each other to some extent. 
In Necturus, the septum is more or less fenestrated and, according 
to Huxley, it is very incomplete in Proteus and Siren, but in all of the 1896.] 
Zoology. 
831 
forms that have been mentioned, as well as in other members of the 
class Batrachia, the sinus venosus opens distinctly into the right auricle 
and the pulmonary vein into the left. 
Let us now compare the heart of a lungless salamander (Fig. 2.) with 
the one just described. The four parts, auricles, ventricle, bulbus arte- 
riosus and sinus venosus are clearly recognizable and, superficially 
examined, present nothing unusual; it is only when the cavities 
are opened that the differences between the two hearts become 
apparent. One of the first things to attract attention is the left auri- 
cle. In the lungless forms examined, it is much smaller in comparison 
to the right than in Diemyctylus, for example, and no pulmonary vein 
was found opening into it. 
The auricular septum has only one opening through it, or perhaps, 
more correctly, it extends only part way across the cavity, but this 
aperture in the septum is so large (Fig. 2, 9.) that it is believed the com- 
munication between the two cavities is more free than even in Necturus. 
Just what function or functions the septum may have in these lungless 
forms, it seems to me, is not quite clear. That it has but little, if any use, 
is indicated by the way the sinus venosus opens into the auricles. In 
place of opening into the right auricle only, as in the forms having lungs, 
it opens more freely into the left auricle than into the right. If the ven- 
tral parietes of the heart be removed, one can look directly into the 
opening of the sinus venosus from either of the auricles, but more 
directly into it from the left than from the right, for when seen from 
the latter, one must look through the large opening of the auricular 
septum, Fig. 2, 9. In salamanders with lungs, each auricle opens in 
common into the ventricle with about equal freedom of communication, 
whereas in the lungless forms the right auricle is in more direct com- 
munication with the ventricle than is the left. 
Judging from the above facts, i. e., the way the sinus venosus opens 
into the auricles, the freedom with which the auricles communicate 
with each other, and the way the auricles communicate with the ven- 
tricle, it would seem as if the heart of the lungless salamanders, functi- 
onally, was only bilocular in place of being trilocular as in the rest of 
the Amphibia. Morphologically, of course, it is trilocular, but whether 
it is so physiologically seems to me doubtful. 
The heart of 8 lungless species have been examined by the writer, 
and so far as was made out, all of them agree closely with the descrip- 
tion as given above. The probabilities are that in all the lungless 
forms similar conditions of the heart will be found. Up to the present 
time 17 speciesand sub-species, either wholly without lungs or with only 832 
The American Naturalist. 
[October, 
functionless rudiments of them, have been reported. In his last paper, 
in which are enumerated 15 of the 17 lungless species, Wilder says that 
" in the Salamandridse lungless species are as numerous as those pos- 
sessing lungs, and that in consequence of this, the definition of the 
group must be modified." It seems, however, that even with his pro- 
posed additions, the definition is still not sufficiently comprehensive, 
for the peculiarities in the structure of the heart certainly have almost 
as profound a significance as the absence of the lungs themselves, and 
should be incorporated in any definition that may be given. In addi- 
tion to the 17 lungless species already mentioned, the writer has found 
an additional one, Spelerpes gluttolineatus. 
In order that one may see at a glance in which families and genera 
lungless individuals are found, the following table, taken from Prof. 
Cope's Batrachia of North America, is appended. [The last column is 
taken from the papers of Wilder and others]. 
No. species without 
Families. Genera. No. of species. 
lungs or with only rudi- 
ments of them. 
Amblystoma (12 [N. A.] 
1 A. opacum 
11 [Siam] 
Amblystomidae - Chondrotus 7 
Linguaelapsus 2 
Dicamptodon 1 
[ Hynobins 5 
Hynobiidae | Salamandrella 2 
[all Asiatic] ■{ Onychodactylus 1 
1 Ranidens 3 
[ Batrachyperus 1 
[P. cinerus 
J P. erythronotus 
[ Plethodon 8 
2 ] P. glutinosus 
Hemidactylium 1 
Batrachoseps 4 
1 B. attenuatus 
Plethoaontidae J 
1 A. lugubris 
Geotriton ? [European] 
1 G. fuscus 
Gyrinophilus 1 
1 G. porphyriticus 
Manculus 2 
1 M. quadridigitatus 
Spelerpes 9 
[ S. bilineatus 
Oedipina 
3 -< S. ruber 
( S. gluttolineatus 
[ Oedipus 9 
Thoriidae -{ Thorius 1 
1 0. variegatus 
Desmognathidae -{ Desmognathus 3 
(D. fusca 
1 j D. f. brimleyorum 
(D. f. auriculatus PLATE XVI. 
Hopkins on Diemyctylus. PLATE XVII. 
Hopkins on Desmognathus. 1896.] 
Zoology. 
833 
Families. 
Salamandridae 
[Old World] 
Genera. 
'Chioglossa 
Salamandra 
Hemisalamandr 
Triturus 
[ Pachytriton 
No. of species. 
1 
3 
a 1 
6 
1 
No. species without 
lungs or with only rudi- 
ments of them. 
Pleurodelidae 
f Salamandrina 
1 
1 S. perspicillata 
[All found in Old _! 
Diemyctylus 
10 [2 N. A. species] 
World; three spe- * 
| Pleurodeles 
1 
cies in N. A.] 
[ Glossolega 
3 
Amphiumidae ■{ Amphiuma 
1 
Coeciliidae -j 
[ (numerous) 
(numerous) 
In the last column of the above table, the figures indicate the num- 
ber of species in which lungless individuals have been found. Where 
there is a discrepancy in the numerals and the number of species fol- 
lowing them, it indicates either sub-species or species not mentioned in 
Cope's Batrachia of North America. 
Fig. 1. Heart of Diemyctylus viridescens (semi-diagramatic) to 
show the general relations of the heart of a salamander with 
lungs. The ventral wall of the heart has been removed in 
order to show the auricular septum, the openings of the sinus 
venosus and the pulmonary vein, and also the relation of the 
auriculo-ventricular aperture to the right and left auricle. 
1. Right auricle; 2. Left auricle ; 3. Ventricle; 4. Sinus 
venosus; 5. Bulbus arteriosus; 6. Auricular septum; 7. 
Auriculo-ventricular aperture; 8. Aperture of sinus ven- 
osus ; 9. Pulmonary vein. 
Fig. 2. Heart of Desmognathus fusca (semi-diagramatic) to show 
relations of the heart in a lungless salamander. The ventral 
wall of the heart has been removed. 
1. Right auricle; 2, Left auricle; 3. Ventricle; 4. Sinus 
venosus; 5. Bulbus arteriosus; 6. Auricular septum; 7. 
Auriculo-ventricular aperture; 8. Aperture of sinus veno- 
sus; 9. Opening through auricular septum. 
G. S. Hopkins, D. Sc., Cornell Univ. 
Description of Figures. 
Reprinted from The American Naturalist, October 1st, 1896.