Using stained acryl latex-injected techniques, the arterial circle of the brain in Acomys cahirinus Desmarest was studied. Results revealed an important individual variability of investigated structure. Three morphological variants were found: (1) the lack of typical arterial circle--opened in front and the back side, (2) partial opened at the back side, (3) completely closed arterial circle. This finding is opposed to many species of mammals, including rodents, and especially laboratory mouse. In our point of view, it seems to be a specific character.

Histological and histochemical investigations revealed that the pterygopalatine ganglion (PPG) in the chinchilla is a structure closely connected with the maxillary nerve. Macro-morphological observations disclosed two different forms of the ganglion: an elongated stripe representing single agglomeration of nerve cells, and a ganglionated plexus comprising smaller aggregations of neurocytes connected with nerve fibres. Immunohistochemistry revealed that nearly 80% of neuronal cell bodies in PPG stained for acetylcholine transferase (CHAT) but only about 50% contained immunoreactivity to vesicular acetylcholine transporter (VACHT). Many neurons (40%) were vasoactive intestinal polypeptide (VIP)-positive. Double-staining demonstrated that approximately 20% of the VIP-immunoreactive neurons were VACHT-negative. Some neurons (10%) in PPG were simultaneously VACHT/nitric oxide synthase (NOS)-or Met-enkephaline (Met-ENK)/CHAT-positive, respectively. A small number of the perikarya stained for somatostatin (SOM) and solitary nerve cell bodies expressed Leu-ENK-and galanin-immunoreactivity. Interestingly about 5-8% of PPG neurons exhibited immunoreactivity to tyrosine hydroxylase (TH). Intraganglionic nerve fibres containing immunoreactivity to VACHT-, VIP-and Met-ENK-were numerous, those stained for calcitonin gene related peptide (CGRP)-and substance P (SP)-were scarce, and single nerve terminals were TH-, GAL-, VIP-and NOS-positive.

The aim of the study was the macromorphological analysis of extrahepatic biliary tract in chinchilla (Chinchilla laniger Molina). Bile ducts, the gall bladder and portal vein were injected with coloured latex. Using the technique of dissection, bile ducts were isolated from the liver lobes. It was found that the cystic duct in this species is rarely single. Hepatic ducts form a system of multiple anastomosing structures running in the hepatoduodenal ligament. Many bile duct openings were observed in the duodenal papilla. The results confirm wide variations of the biliary tract in mammals and may be important for comparative analysis of the morphological differentiation of these structures in small mammals.

Using the thiocholine method and histological techniques the myenteric plexuses of pigeon and hen were studied. Investigations revealed the presence of a nervous network in the wall of the small intestine of both animals. It consists of many nerve fibres crossing each other and creating meshes in a variety of shapes. The density of the network was different according to the species and to the parts of intestine. The myenteric plexus from the pigeon's duodenum is thicker (3.7-fold) than in the remaining part of the small intestine; in the hen this is approximately 2.2-fold thicker. The meshes of the duodenum in both species are smaller than in the jejunum and ileum. The results of histological investigations showed different localization of myenteric plexuses; in pigeon in the space between the circular and longitudinal muscle layers, and in hen within the circular muscle.

Using the thiocholine method and histological techniques, the topography and morphology of cardiac ganglia in midday gerbil, Egyptian spiny mouse, chinchilla laniger and pigeon were studied. The results demonstrated that cardiac ganglia in all investigated species are embedded in epicardial fat. They formed plexo-ganglionic structures. Each of them composed of many ganglia (from seven up to 36) different in size and shape, and interconnected by fascicles of nerve fibres. Comparative analysis showed that the density of neural network and cell aggregations was different in individual species. The richest plexo-ganglionic structure was in pigeon. It was organized in three plexo-ganglia with an average of 30 ganglia. The largest one was located along the anterior interventricular sulcus. The cardiac ganglia of investigated mammals were localized mainly on the epicardium of atria; in Egyptian spiny mouse and chinchilla laniger on the ventral surface of right atrium, but in midday gerbil on the dorsal surface of left atrium. Moreover, in midday gerbil and Egyptian spiny mouse the little plexo-ganglionic structure on the ventricle were noticed. Additionally, in midday gerbil the single nerve cells might be observed between cardiac muscle of atria. It can be said that, the strongly developed cardiac plexus in pigeon is probably connected with his behaviour and functional properties of the heart. The arrangement of neurones in cardiac ganglia of all examined mammals was uniform over the whole surface of the sections, while in the pigeon, neurones were located mainly in the peripheral part of the ganglion.