It is proposed that the Harderian glands are those ocular glands that have tubuloalveolar endpieces with wide lumina and secrete lipid by a merocrine mechanism.
The Harderian gland occurs in various mammals, not only in eutherias but also in marsupials. However, as the gland has hereto-fore been studied almost exclusively in rodents and lagomorphs, it should be studied more in other groups of mammals, especially primitive mammals such as marsupials and insectivores.
The secretory duct of the mammalian Harderian gland, as a rule, is single and opens near the third eyelid in the inner canthus. The whale Harderian gland is an exception as it is present as two masses and each of which has multiple excretory ducts. In rodents and lagomorphs, the orbital venous sinus is very well developed and surrounds almost all the orbital contents. Therefore, the surface of the gland is macroscopically smooth.
Histologically, the gland has branched tubuloalveolar endpieces with wide lumina, and rarely has a duct system. It is quite difficult to detect a duct in usual histological sections. In rodents, the alveoli often contain two types of glandular cells, however, the significance of the difference between these two types is quite uncertain.
The Harderian gland is the sole example in which glandular cells secrete lipid by a merocrine mechanism. The formation process of the secretory vacuoles within glandular cells is not known.
In rodents and lagomorphs, the lipid of the gland is mainly either glyceryl ether diesters or wax esters, and similar to sebum. In rodents, the gland often contains porphyrin, but its significance is quite uncertain.
The function of the Harderian gland probably varies among mammals. In aquatic mammals, the glandular secretion is thought to protect the eye from sea water. In rodents and lagomorphs, the gland may serve either as a sebaceous or a pheromonal gland.
It appears most probable that phylogenetically the mammalian Harderian gland originated from the lacrimal gland of ancestral mammals from which all marsupials and eutherias have descended.

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Effects of hydrocortisone on peritoneal free cells in the mouse were examined by quantitative morphologic procedures.
Mice of both sexes at 60 to 65 days of age received one, two, or four successive subcutaneous injections of 0.5mg hydrocortisone every 24hrs. After one injection, peritoneal free cells showed a rapid decrease in number during the first 3hrs. They then increased up to about 1.5 times the control value at 24hrs and returned to the normal level at 48hrs in both sexes. After two injections, peritoneal cells showed a significant decrease in number in females during the first 2 days. Thereafter they returned to normal in both sexes at 8 to 12 days.
The three major types of peritoneal cells, type I, II and III cells, which have been described in pervious papers (ABE et al., 1979a, b; HONMA et al., 1980), differed in response to hydrocortisone. Type I cells (small lymphocytes) were markedly reduced in number immediately after hydrocortisone injection and remained depleted even 12 days after injection. Type II cells (medium-sized mononuclear cells) showed the most remarkable response to hydrocortisone. Changes in the total number of peritoneal cells following hydrocortisone injection were ascribed mainly to those of type II cells. Type III cells (macrophages) did not show any significant changes in number after injection.

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The fine structures and distributions of the tight and gap junctions in guinea-pig bile canalicules were examined by the freeze-fracture replica method. In order to correlate the structure and function of the cell junctions the guinea-pig hepatocytes were studied by electron microscopy after ligation for 6-96hr of the hepatic common duct, and partly after recanalization.
The junctional structures in a normal condition were characterized by fine configurations of fully formed tight junctional networks and gap junctions. Duct ligation caused: 1) reduction in number of the tight junctional strands, enlargement of the tight junctional compartments, and sudden appearance of gap junctions near the tight junction network; 2) the disruption of the tight junctional strands into small clusters; 3) abluminal stretching of focal strands, often continuous with the gap junctions; 4) sudden disappearance of the gap junctions late after ligation; 5) particle aggregates surrounded by or integrated in the tight junctional strands, which were considered as “reserve aggregates”; and 6) extremely disordered tight junction networks without any gap junctions, indicating a leaky pattern. Recanalization was followed by 1) prompt reassembly of tight junctions with abundant desmosomes, and 2) delayed appearance of gap junctions.
It is suggested that jaundice may occur in the following way: soon after the duct ligation, bile may leak through the disrupted tight junction networks, and dilatations of the intercellular space may affect the dissociation of the gap junctions; such regurgitation of the bile through the space of Disse may cause bilirubinemia. It is suggested that the reconstitution of the junctional complexes may occur in the following way: soon after the release from the obstruction, the reserve aggregates of intramembraneous particles may be scattered to repair the disrupted tight junction networks lacking in diverse gap junctions, and, with the later appaerance of gap junctions, the junctional complexes are completely repaired. These morphological features coincide with the results of biochemical examination of the serum bilirubin levels of the guinea-pigs.

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By using immunoperoxydase techniques, it was demonstrated that the lymph follicles, formed in the thymic medulla of castrated DA rats after 20 injections with typhoid-paratyphoid bacilli at 10 day intervals, were composed mainly of B lymphocytes.

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The Ito cell (fat-storing cell) in the liver of the lizard, snake and turtle was studied by electron microscopy. The Ito cell was positioned in the perisinusoidal space of Disse and contained characteristic fat droplets in all of the animals studied. The fat droplets in the Ito cells of turtles, fed commercially obtained pig liver, were numerous and large. The Ito cells contained fewer and smaller fat droplets in the lizards and snakes, caught in their natural habitat and sacrificed. There were frequently Ito cells without fat droplets, designated as empty Ito cells, in the snake liver. Dilated cisternae of rough endoplasmic reticulum were found in the Ito cells of the lizard and snake liver, but they were absent from the Ito cells of the turtle liver. It is suggested that the nutritional state of animals, especially the vitamin A concentration in the food, might induce these differences in the Ito cell.

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The submandibular glands of adult female and male Japanese wood mice (Apodemus ainu ainu TOKUDA) were studied histochemically using toluidine blue (pH 2.5, 4.1 and 7.0, McIlvaine), PAS reaction, Millon's reaction for tyrosine, p-dimethylamino-benzaldehyde for tryptophan, and substrate film techniques for amylase and protease. The glands were also examined ultrastructurally and ultracytochemically by the periodic acid-thiocarbohydrazide-silver proteinate technique (PA-TCH-SP staining) for glycoprotein. The submandibular gland consisted of the striated ducts (SDs), the convoluted granular tubules (CGTs), the intercalated ducts and the terminal portions. In both sexes the acinar cells were seromucous in secretory nature, and the secretory granules contained glycoproteins and were negative to amylase and protease activities. By the PA-TCH-SP staining, the distribution of glycoproteins and fine structural alternations corresponding to the maturation of the secretory granules were demonstrated. The granules of the CGT cells contained tryptophan, tyrosine and neutral mucopolysaccharides. The granules showed negative reactions to acid mucopolysaccharides, protease and amylase activities, and glycoproteins. Glycogen particles in the apocrine processes were intensely positive to PA-TCH-SP staining. Dark and clear cells were distinguished in the SDs. The apical cytoplasm of the SD cells contained two types of vesicles. One type may represent reabsorption vesicles and the other secretory vesicles. Some of the SD cells had both microvilli, associated with reabsorption vesicles and apocrine process containing abundant glycogen particles on their luminal surface. From the statistical analysis of the average values, the CGT diameter of the male mice was significantly larger than that of the female mice.

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