This book is a comparative study of two types of tuberculosis bacilli: those that infect mammals (bovine), and those that infect humans. The author, a renowned medical scientist, presents findings from a meticulous and extensive investigation into the distinct characteristics of these two types of bacilli. Through an array of experiments, the author sheds light on the variations in their virulence, growth patterns, and impact on the immune systems of different species. The significance of these distinctions extends beyond scientific curiosity; they have critical implications for understanding the transmission of tuberculosis between animals and humans, as well as for the development of diagnostic tools, treatments, and preventive measures. The book not only deepens our knowledge of the tubercle bacillus but also underscores the importance of ongoing research in understanding and combating infectious diseases.