1. This paper deals with the morphological and physiological studies on the branchial gland of Octopus, especially O. vulgaris.
2. Since it seems safe to assign endocrine function to the branchial gland, new terminology like branchialectomy, abranchialism, branchial deficiency etc. has been introduced.
3. The branchial gland is slightly heavier in female than in male in the three species of Octopus examined.
4. There are two veins (afferent and efferent) and an artery supplying blood to the branchial gland; the efferent vein (vena branchio-lienalis) serves to transport the secretion of the gland.
5. No nervous supply is present in the glandular part of the organ.
6. The branchial gland is an organ of mesodermal origin; in the embryonic stage it appears in the axis of the gill.
7. Histologically observed, the distribution of the veins favours the transport of the secreted substance.
8. The cytoplasm of the gland cell is characterised by its basophily and extreme softness, and great liability to shrinkage by fixatives.
9. The secretory globule is acidophilic.
10. The ligature of the efferent vein does not give much injury on the animal, because the active principle can be transported by other vessels.
11. Unilateral extirpation of the branchial gland does not give a noticeable ill effect on the animal.
12 Total extirpation of the branchial gland is always fatal to the animal.
13. Symptoms of deficiency of the branchial gland are as follows:
a. Loss of appetite,
b. suppression of growth,
c. decrease of regenerating power,
d. decrease of respiratory frequency,
e. muscular inertia,
f. injury in the integument,
h. fall of blood pressure,
i. edema formation in the connective tissue,
j. degeneration of the ovary,
k. decrease of nervous activity, resulting stupor,
l. low general vitality.
14. Histological examination of the operated animal shows the conspicuous atrophy of all tissues.
15. So long as the branchial gland is not injured, the effect of inanition, castration or artificial anaemia is rather slight.
16. Repeated injection of the extract of the branchial gland into branchialectomised animals saves to some extent the lesion of branchial deficiency.
17. Repeated injection of the extract of the branchial gland into intact animals causes intoxication.
18. An alcoholic extract of the branchial gland activates the function of the circulatory system of an octopus.
19. Administration of the extract of the branchial gland into a mouse is ineffective.
20. Administration of the extract of the branchial gland is slightly effective on the growth of a frog tadpole.
21. The active principle of the branchial gland stands boiling and can be extracted with alcohol.
22. Transplantantion of an excised piece of the branchial gland was unsuccessful.
23. The animal having an abnormally small branchial gland shows low vitality.
24. Local anaemic infarcts are often found in the branchial gland; when such infarcts are numerous, the animal is weakened.
25. The part of an infarct is in the state of necrosis.
26. The infarct appears also in the branchial heart, possibly caused by the same lesion in the branchial gland.
27. The infarct can be recovered by the absorption of a necrotic tissue and regeneration.
28. The cause of the infarct is due to the morphological and physiological characteristics of the branchial gland.
29. Colouration in life, and post-mortem discolouration of the branchial gland are described, which seem to be due to the oxidation of the secretion.
30. The branchial gland in Cephalopods has probably a function somewhat similar to that of the medulla of the adrenal gland in vertebrates.
31. So far as our present knowledge goes, the branchial gland is one of the largest endocrine organs in Cephalopods, as well as in all invertebrates.