The important maxillary sinus cannot well be shown. It is found within the maxillary bone (cheek bone). The inner end of the line marked Nasal cavity locates it.
It forms the floor of the thorax (chest) and the roof of the abdomen. It is attached by a strong tendon to the spinal column behind, and to the walls of the thorax at its lowest part, which is below the ribs. In front its attachment is to the cartilage at the pit of the stomach. It also connects with the transverse abdominal muscle. The diaphragm being convex, in inspiration the contraction of its fibres flattens it downward and presses down the organs in the abdomen, thus increasing the depth of the thorax. Expiration depends wholly on other muscles.
Vertical section of the skull
The basic principle of life, in the Galenic physiology, is a spirit, anima or pneuma, drawn from the general world-soul in the act of respiration. It enters the body through the rough artery (τραχεῖα ἀρτηρία, arteria aspera of mediaeval notation), the organ known to our nomenclature as the trachea. From this trachea the pneuma passes to the lung and then, through the vein-like artery (ἀρτηρία φλεβώδης, arteria venalis of mediaeval writers, the pulmonary vein of our nomenclature), to the left ventricle. Here it will be best to leave it for a moment and trace the vascular system along a different route.
The idea of a close parallelism between the structure of man and of the wider universe was gradually abandoned by the scientific, while among the unscientific it degenerated and became little better than an insane obsession. As such it appears in the ingenious ravings of the English follower of Paracelsus, the Rosicrucian, Robert Fludd, who reproduced, often with fidelity, the systems which had some novelty five centuries before his time.
An anatomical diagram of about 1298
The first printed picture of dissection
The figure shows a professor and pupil. The former is demonstrating the bones of a skeleton.