And there are numerous other factors that indicate our relationship to water-dwelling animals, were it no more than the fact that the human embryo has a gill arch, which alone would provide sufficient evidence that we can trace our ancestry back to aquatic organisms. The bone tissue of humans and animals consists of an organic solution, which when boiled produces a glue containing inorganic salts, principally calcium carbonate, but also composites of fluorine and magnesium. All these chemicals are found in solution in the sea, which is a further indication that land animals originally descended from sea creatures. The composition of blood also points the same way, for, as is well known, serious loss of blood can to a large extent be compensated for by using a 0.9 per cent saline solution, while pure diluted seawater has been successfully employed for the same purpose. Finally, it seems highly probable that far from being descended from the same species of mammal as the other animals that share dry land with him, man has from the beginning represented a unique branch of the mammal family.
