Inspection shows the degree of fulness or collapse, and also the existence or absence of what has been termed venous pulse.
Venous pulse occurs only at the lower extremity of the jugulars. It is very frequent in animals of the bovine species, and in thin animals is not necessarily a pathological symptom. It is due to reflux of blood in the anterior vena cava, under the influence of the expiratory effort; sometimes to emphysema, tuberculosis, etc.; in other cases to the return of blood towards the vena cava and jugulars at the moment of auricular systole, as a result of lesions of the tricuspid or auriculo-ventricular orifices.
By palpation of the veins their permeability can be estimated, also the degree of distension or obstruction, and the condition of their contents.
Capillary system. Among methods of arriving at the state of the circulatory system must be included an examination of the vascular condition of the accessible mucous membranes, such as those of the eye, mouth, nostril, vulva, etc. This examination is easy to carry out, and is of value in diagnosing congestive states, pneumonia, and local inflammation.
Blood. Examination of the blood is sometimes necessary for the exact diagnosis of certain diseases, and therefore should be carried out whenever occasion requires. The physical state, coloration, and rapidity of coagulation afford valuable data in certain diseased conditions, and indicate the approximate richness in hæmoglobin, the normal or abnormal composition of the plasma, and the richness of the blood in white corpuscles.
Microscopic examination is still more valuable, whether carried out by the moist method, in which a drop of blood is compressed under a cover glass, or the dry method with or without staining. In the latter case the specimen is fixed with a mixture of equal parts of alcohol and ether or by immersing it in a 1 per cent. solution of osmic acid.
By this means it is possible to detect the condition of the red and white blood corpuscles and hæmatoblasts; the existence or non-existence of leucocytosis and its degree, as well as the existence, for instance, of leucocythæmia.
The blood corpuscles may also be counted.
Histological examination, supplemented by suitable staining, reveals the presence of normal or abnormal blood corpuscles, parasites such as piroplasma, or microbes such as bacteria.
Such examination necessarily presupposes a knowledge of what should be looked for in the normal state.